Skip to main content
PMC home page
PLOS ONE logoLink to PLOS ONE
. 2020 Jul 21;15(7):e0223087. doi: 10.1371/journal.pone.0223087

Distribution of Human T-Lymphotropic Virus (HTLV) and Hepatitis C Co-infection in Bahia, Brazil

Felicidade Mota Pereira 1,2, Maria da Conceição Chagas de Almeida 3, Fred Luciano Neves Santos 1, Roberto Perez Carreiro 4, Bernardo Galvão-Castro 1,5, Maria Fernanda Rios Grassi 1,5,*
Editor: William M Switzer6
PMCID: PMC7373273  PMID: 32692782

Abstract

Both Human T-lymphotropic virus type 1 (HTLV-1) and hepatitis C virus (HCV) are endemic in Brazil. In Salvador, the capital of the state of Bahia, 2% and 1.5% of the general population is infected with HTLV-1 or HCV. This study aimed to estimate the prevalence and the distribution of HTLV/HCV coinfection in Bahia. This cross-sectional study was conducted at the Central Laboratory of Public Health for the state of Bahia (LACEN-BA). All samples in the LACEN database submitted to serological testing for anti-HCV (chemiluminescence) and anti-HTLV-1/2 (chemiluminescence/ELISA and Western blot) from 2004 to 2013 were included. Infection rate was expressed as the number of infected individuals per 100,000 inhabitants in a given municipality; municipalities were grouped by microregion for further analysis. A total of 120,192 samples originating from 358 of the 417 municipalities in Bahia (85.8%) were evaluated. The overall HCV coinfection rate in HTLV-positive was 14.31% [2.8 (ranging from 0.4 to 8.0) per 100,000 inhabitants.] Twenty-one (5%) of the municipalities reported at least one case of HTLV/HCV coinfection. Most cases (87%) were concentrated in three microregions (Salvador: 79%, Ilhéus/Itabuna: 5%, Porto Seguro: 3%). Coinfection occurred more frequently in males (51%) with a mean age of 59 [(IQR): 46–59] years. HTLV/HCV coinfection in the state of Bahia was more frequently found among males living in the microregions of Salvador, Ilhéus/Itabuna and Porto Seguro, all of which are known to be endemic for HTLV infection.

Introduction

Both human T-Lymphotropic virus (HTLV) and hepatitis C virus (HCV) are transmitted by parenteral exposure to contaminated blood or blood products [1–3]. In addition, HTLV can be transmitted sexually [4] and vertically from mother-to-child, predominantly through breastfeeding [5, 6]. HTLV type 1 (HTLV-1) is endemic in several parts of the world, with an estimated 5 to 10 million people harboring this virus [7]. In Brazil, the prevalence of HTLV-1 varies according to geographic location, with the North and Northeast regions being the most affected [8]. Recently, it was reported that HTLV-1 is widespread throughout the state of Bahia, with at least 130,000 individuals infected with this virus [9]. While HCV infection affects around 2.5% of the world's population (177.5 million adults), a population-based study in Brazil focusing on all 26 state capitals and the Federal District found an overall HCV seroprevalence of 1.38% [10]; in Salvador, 1.5% of the general population is estimated to be infected with HCV [11].

In some regions endemic for HTLV infection, such as Asia and sub-Saharan Africa, the prevalence of HTLV/HCV coinfection in urban areas can reach up to 28% [12–15]. However, this coinfection has not been reported in Ethiopian rural areas [16]. In Europe, where the rate of HTLV infection in the general population is below 0.1% [7], although no reports of HTLV-1/HCV coinfection have been published to date [17, 18], HTLV-2/HCV coinfection was reportedly found in injecting drug users [19].

Brazil is endemic for both HTLV and HCV, and the presence of coinfection has been rarely reported in HCV patients undergoing treatment, as well as in blood donors, especially those in Southeastern Brazil. The prevalence of HTLV in individuals infected with HCV ranges from 5.3% in São Paulo [20] to 7.5% in Rio de Janeiro [21]. In addition, in blood donors, HCV was found in 35.9% of first-time HTLV-positive blood donors [22].

Contradictory clinical outcomes in the course of HTLV/HCV coinfection have been reported in Brazil and Japan. A better prognosis was described in coinfected Brazilian individuals who presented higher levels of Th1-type cytokines and CD4+ T lymphocytes, as well as lower hepatic fibrosis and alanine aminotransferase (ALT) [23–26]. Conversely, a Japanese study involving coinfected individuals described higher viral loads, a more rapid progression to hepatocellular carcinoma and a decreased response to treatment with interferon [15, 27–30]. In light of considerations regarding the influence of HTLV/HCV coinfection on the outcome of either infection and a lack of epidemiologic studies, notably in the Brazilian Northeast macroregion, the present study aimed to determine the rate of coinfection throughout the state of Bahia and map the geographical distribution of cases over a 10-year period.

Materials and methods

Ethics statement

The Institutional Review Board (IRB) for Human Research at the Gonçalo Moniz Institute of the Oswaldo Cruz Foundation (Salvador, Bahia, Brazil) provided ethical approval to conduct this study (CAAE number 22478813.7.0000.0040). In order to maintain patient information confidentiality, data were fully were anonymized so that the researchers do not have access to patient’s individual information avoiding the need for verbal or written consent.

Study area

The present study was carried out in the state of Bahia, Brazil, the fourth largest state in terms of population size (15,203,934 inhabitants), and the fifth-largest in terms of area: 564.722,611 km2. Bahia is comprised of 417 municipalities, which are grouped into 32 microregions and seven mesoregions according to economic and social similarities by the Brazilian National Institute of Geography and Statistics (IBGE) (http://www.ibge.gov.br).

Study design

The present ecological retrospective study was using data obtained from the Central Laboratory of Public Health of Bahia (LACEN-BA), which is responsible for the laboratory analysis of infectious disease surveillance throughout the state. The population served by LACEN mainly consists of individuals who exhibit symptoms of infectious disease, pregnant women and individuals referred by blood blanks, the prison system or public health units distributed throughout the state of Bahia. Individuals were included if submitted to serological testing for both HTLV and HCV, either concomitantly or in isolation, from 2004 and 2013. Any indeterminate confirmatory test results were excluded from the present analysis.

Laboratory testing

Serology for HTLV was performed at LACEN using the Murex HTLV-1/2 kit (DiaSorin SpA, Dartford, UK) from 2004 to 2008, the anti-HTLV-1/2 Sym Solution kit (Symbiosis Diagnostica LTDA, Leme, Brazil) from 2009 to 2010 and by microparticle CLIA chemiluminescence (Architect rHTLV-1/2, Abbott Diagnostics Division, Wiesbaden, Germany) from 2011 on. Confirmatory Western blotting (HTLV Blot 2.4, Genelabs Diagnostics, Singapore) was performed for all samples presenting seroreactivity. Serology for HCV was performed at LACEN by microparticle enzyme immunoassay (MEIA; AxSYM Anti-HCV Abbott Diagnostics Division, Illinois, USA) from 2004 to 2007, and thereafter by chemiluminescent microparticle immunoassay (Architect Anti-HCV, Abbott Diagnostics Division, Wiesbaden, Germany). With respect to molecular testing, RT-PCR (AMPLICOR MONITOR®, Roche Molecular Systems, Branchburg, NJ, USA) was employed in accordance with the manufacturer's specifications. Genotyping was performed by analyzing the highly conserved 5’ untranslated region using the Linear Array Hepatitis C Virus Genotyping Test (LiPA—Line Probe Assay—Roche Diagnostics, USA), following the manufacturer’s guidelines. This assay allows for the determination of six genotypes and subtypes (1a, 1b, 2, 2a, 2b, 3, 3a, 4, 4c, 5, 5a and 6).

Data analysis

The SMART LAB laboratory management system was used to extract data from all serological HTLV and HCV tests performed throughout the study period, considering all individuals who were submitted to at least one HTLV and one HCV test. To avoid duplication, the most recent available serological results were considered. Each individual’s unique registration number was considered as the key variable. The resulting database was validated using the R software package and analyzed with STATA v13.0. With regard to age, median and interquartile range (IQR) intervals were calculated and individuals were grouped accordingly. The prevalence of HTLV / HCV coinfection was determined by taking into account the presence of HTLV and HCV antibodies. The presence of anti-HTLV indicates infection, while the presence of anti-HCV might indicate exposure and / or infection. The rate of coinfection the primary outcome and was expressed as the number of individuals infected per 100,000 inhabitants. Digital maps detailing municipalities and microregions were obtained from the IBGE cartographic database in shapefile (.shp) format, and reformatted and analyzed using TerraView version 4.2 software freely provided by the National Institute for Space Research (www.dpi.inpe.br/terraview).

Results

A total of 120,192 individuals were submitted to both anti-HCV and anti-HTLV 1/2 serology sometime from 2004 and 2013 (S1 Table). The median age of the studied population was 40 years [interquartile range (IQR): 25–41 years] and the female:male ratio was 7:1. The 861 HTLV-positive samples submitted to confirmatory Western blotting produced 713 [0.6%, 95%CI: 0.55–0.64, (713/120,192)] results with seroreactivity for HTLV: 641 (90%) were positive for HTLV-1, 29 (4.0%) for HTLV-2, and 43 (6%) were positive for both HTLV-1 and HTLV-2. The 148 (17.2%) indeterminate serologies were excluded from all further analysis (Fig 1).

Fig 1. Flow chart detailing the classification protocols employed in the studied population to determine HTLV and HCV infection status.

Fig 1

Open in a new tab

HCV infection was detected in 14.2% (101/713; 95% CI: 11.9–17.1) of the HTLV-positive individuals, versus 0.72% (855/119,331; 95% CI: 0.67–0.77) of the HTLV-negative samples, p< 0.0001 (OR: 22.9; CI: 18.3–28.5) (Fig 1). With regard to coinfection, HCV infection was detected mainly among HTLV-2 (37.9%) infected individuals, followed by HTLV-1 (13.3%) and HTLV-1/2 (11.6%). The HTLV infection prevalence in the 120,192 individuals submitted to both anti-HCV and anti-HTLV-1/2 was substantially higher in women than in man subjects (75.6% vs. 24.4%, p < 0.001). The coinfection rate was more frequent in men (~30%, 52/174; p< 0.0001) compared to women (~9%, 49/534). The median age of cases de HTLV/HCV was 59 years [interquartile range (IQR): 46–59 years]. No age was registered for 16 coinfected individuals (Table 1). The genotype of HCV was identified in 31 out of 101 coinfected individuals. Gentotypes 1 (87%) and 3 (13%) were the most frequently identified.

Table 1. Profile of HTLV/HCV coinfection in municipalities located in Bahia, Brazil from 2004 to 2013.

Municipality Population* Microregion # performed tests (%Female) # cases Age %Female Rate**
Terra Nova 12,467 Catu 224 (98) 1 46 0 8.02
Itagi 14,084 Jequié 151 (87) 1 48 100 7.10
Biritinga 14,129 Serrinha 580 (97) 1 32 100 7.08
Ipiaú 43,169 Ilhéus/Itabuna 1,496 (91) 2 57 0 4.63
Itabela 26,228 Porto Seguro 323 (93) 1 47 0 3.81
Camacan 30,677 Ilhéus/Itabuna 647 (70) 1 66 0 3.26
Esplanada 31,852 Entre Rios 517 (98) 1 47 100 3.14
Morro do Chapéu 34,276 Jacobina 1,464 (92) 1 27 100 2.92
Vera Cruz 35,951 Salvador 231 (94) 1 56 100 2.78
Senhor do Bonfim 73,955 Senhor do Bonfim 1,016 (74) 2 30 50 2.70
Salvador 2,920,679 Salvador 30,001 (81) 78 54£ 44.8 2.67
São Sebastião do Passé 40,972 Catu 140 (86) 1 39 100 2.44
Ipirá 60,891 Feira de Santana 2,831 (93) 1 50 0 1.64
Brumado 63,391 Brumado 276 (93) 1 40 100 1.58
Guanambi 77,691 Guanambi 595 (89) 1 51 0 1.29
Santo Antônio de Jesus 86,014 Santo Antônio de Jesus 1,644 (68) 1 51 100 1.16
Ilhéus 219,927 Ilhéus/Itabuna 201 (56) 2 NA 50 0.91
Porto Seguro 117,402 Porto Seguro 306 (86) 1 60 100 0.85
Teixeira de Freitas 121,268 Porto Seguro 1,181 (85) 1 63 100 0.82
Lauro de Freitas 147,661 Salvador 2,619 (87) 1 52 100 0.68
Juazeiro 234,082 Juazeiro 93 (71) 1 33 100 0.43
TOTAL 101 2.8
Open in a new tab

Mean age (years)

*Mean population from 2008 to 2009 (www.ibge.gov.br).

** No. of cases per 100,000 inhabitants.

£ Mean age calculated from data available for 64 individuals.

Out of the 417 state municipalities, 358 (85.8%) sent samples to LACEN at some point during the study period. Information regarding sample origin was absent for 1.2% of the analyzed samples. The overall rate of HTLV/HCV coinfection was estimated at 2.8 per 100,000 inhabitants (range from 0.43 to 8.02 per 100,000 inhabitants). At least one case of HTLV or HCV infection was reported in 135 and 123 of the municipalities, respectively (Fig 2). Regarding the geographical distribution of coinfected HTLV/HCV cases, 21 (5.03%) municipalities presented at least one occurrence of coinfection. The majority of cases were concentrated in just three microregions: Salvador (80/101 cases), Ilhéus/Itabuna (5/101 cases) and (Porto Seguro (3/101 cases) (Table 1 and Fig 2). In the Salvador microregion, 78 out of 80 cases of coinfection with both HTLV and HCV were concentrated the municipality of Salvador, followed by the municipalities of Ilhéus and Ipiaú (both located in Ilhéus/Itabuna microregion) with two identified cases each (Table 1).

Fig 2. Geographic distribution of HTLV and HCV cases among the municipalities in the state of Bahia from 2004 and 2013.

Fig 2

Open in a new tab

Microregions are delimited by white lines. The three microregions with the highest concentrations of coinfection cases are highlighted by arrows.

Discussion

The present study represents the first analysis of HTLV/HCV coinfection performed in the entire state of Bahia, which is considered endemic for both HTLV and HCV infections [11, 31]. A total of 14.2% of the HTLV-infected individuals investigated herein were found to be coinfected with HCV, resulting in an overall coinfection prevalence of 2.8/100,000 inhabitants. Although isolated infection with HTLV or HCV was disseminated throughout the state’s microregions, the majority of HTLV/HCV coinfection cases clustered in just three microregions: Salvador (79% of cases), Ilhéus/Itabuna (5% of cases) and Porto Seguro (3% of cases). Of note, the Salvador microregion, which boasts a population of more than 3.4 million inhabitants, had the largest absolute number of coinfected individuals. This result was expected, since population-based studies conducted in this city reported that around 2% and 1.5% of individuals are infected with HTLV-1 and HCV, respectively [11, 31]. Salvador and the neighboring municipalities located around the Baía de Todos os Santos (Bay of All Saints) comprise a region that was historically heavily engaged in slave trading from the 16th to 19th centuries. Nowadays, the local population is mainly of African descent. The economy is based on commercial, service, and industrial activities. In the Ilhéus-Itabuna and Porto Seguro microregions, both located in the southernmost region of the state, tourism and commercial activities are essential to the local economy. Recently, these two microregions were highlighted as significant foci of HTLV-1 infection [9].

The present study sought to determine the prevalence of HCV infection in a sample of HTLV-infected individuals. In Brazil, epidemiological data on the rate of HTLV/HCV coinfection remains scarce. Only three studies that estimated the prevalence of HTLV/HCV coinfection were recovered in the scientific literature: one in the city of São Paulo and one in the city of Rio de Janeiro, both studies evaluated the coinfection of HTLV / HCV in individuals undergoing HCV treatment [20, 21]. The third study was performed in the city of Ribeirão Preto (São Paulo) and evaluated for 11 years the seroprevalence of HTLV and co-infections with other sexually transmitted diseases such as HIV, syphilis and HBV [22]. In the first two studies, the denominator was the number of HCV cases, in the last one the denominator was the number of HTLV cases. Our study is similar to studies conducted in Japan, in which the prevalence of HTLV / HCV coinfection was estimated in HTLV endemic areas [12, 15] and in donor donors blood from Ribeirão Preto [22]. In contrast to our analysis, previous studies have evaluated HTLV infection in individuals with hepatitis C who received treatment [20, 21]. We found that HTLV-positive individuals presented a significantly higher prevalence for anti-HCV and also had a higher probability of acquiring hepatitis C (OR: 22.9) compared to HTLV-negative individuals. Similar results were obtained on Iki Island in Japan, an endemic region for both viruses [12]. However, this difference was not observed in a study conducted in two southern Japanese villages, where HTLV and HCV are endemic [15].

Throughout the study period, the testing methodology for both HTLV and HCV was updated from ELISA to chemiluminescence assays. Nonetheless, both tests offer similarly high sensitivity and specificity. Recent studies evaluating the performance of these methods indicate improved accuracy using chemiluminescence, both in HTLV [32] and HCV serology [33], i.e. both can be effectively used for serological screening in the laboratory diagnosis of HTLV and HCV. Chemiluminescence is mainly used by the laboratories that analyze a large number of samples, as this technique reduces time needed to produce results and minimizes errors in analysis.

In the present study, males over 50 years were predominantly found to be coinfected with HTLV and HCV, which is consistent with reports from other studies [20, 34, 35]. Moreover, it is known that the prevalence of HTLV-1 infection increases with age [31]. The advanced age of coinfected individuals was expected, since both HTLV and HCV have a long asymptomatic course, and the diagnosis of these infections often only occurs when chronic complications are present. In addition, since screening for both viruses only became mandatory at blood banks beginning in 1993, prior to this period, poor sterilization in the reuse of glass syringes was frequent, which contributed to increased transmission of HCV [36], and possibly also HTLV. Although the present study did not attempt to determine the routes of infection in co-infected individuals, it is possible that the sharing of needles and syringes was responsible for infection in these cases [10, 20, 34, 37, 38]. In HCV, which is transmitted through exposure to blood, particularly by transfusion, organ transplantation of infected individuals [39], injected drug use is considered the leading risk factor for virus acquisition [10, 40]. In contrast, HTLV-1 infection occurs more frequently by sexual route and breastfeeding, both uncommon in HCV transmission [41].

In the context of HTLV/HCV coinfection, the present study found a higher proportion of HTLV-2 in coinfected individuals. HTLV-2 infection has been mostly reported among injecting drug users in urban areas [8] and in indigenous populations in northern Brazil [42]. Achieving an accurate discrimination between HTLV-1 and HTLV-2 may have prognostic value in the outcome of HCV [20]. Some clinical complications, such as increased HCV load, hepatocyte damage, hepatocarcinogenesis, high levels of alanine aminotransferase (ALT) and increases in the spontaneous production of IL-1, IL-2 and IFN-γ, have been more frequently reported in individuals coinfected with HTLV-1/HCV than those with HTLV-2/HCV [23, 25, 26, 29, 34, 40, 43].

Regarding molecular testing, out of 101 HTLV/HCV-coinfected individuals included, only 40 records contained information regarding molecular investigation (RNA-HCV), and 31 of these were submitted to HCV genotyping. The Brazilian Ministry of Health protocol recommends genotyping for patients who are initiating treatment, as well as those undergoing treatment who present resistance to antivirals [44]. With respect to the profile of HCV circulating genotypes, the present study detected the presence of Genotypes 1 and 3, in 31 coinfected individuals. The most prevalent genotype was type 1 (83%). Accordingly, the HCV genotypes 1 and 3 are the most prevalent worldwide, accounting for about 46.2 and 30.1% of infections, respectively [45]. However, a low number of HCV genotype samples were tested, possibly leading to a misinterpretation of results, since the HCV clearance rate may vary in HTLV infected persons and by genotype.

The main limitation of the present study was the use of non-random sampling, which resulted in a predominance of females. In the state of Bahia, serological HTLV screening for pregnant women is compulsory since 2011, which could thusly contribute to a higher proportion of women in the samples analyzed. However, the robust representation of cases reported throughout the state’s municipalities, as well as the absolute number of individuals analyzed, provide an overview of the circulation of HTLV and HCV in the state. Another limitation is using anti-HCV serology instead HCV-RNA measurement to determine the prevalence of infection. Different of HTLV, infection by HCV may be spontaneously cleared and treated. However, anti-HCV is the most common marker of hepatitis C infection, used to estimate its prevalence globally. In Brazil, it is one of the markers used to report cases of HCV infection in the SINAN [44]. Other studies previously conducted to estimate the prevalence of hepatitis C infection in Brazil and worldwide have also used anti-HCV for this purpose [8, 10, 46]. In the present study, we had information on RNA-HCV data for 40 HTLV/HCV-coinfected individuals. Of these, 32 had detectable viral load.

In conclusion, the present study evaluated a large number of individuals in Bahia, considered one of the states in Brazil most affected by HTLV infection. We found that at least 14% of the individuals infected with HTLV also harbor HCV. Coinfection was concentrated in males who resided in the microregions of Salvador, Ilhéus-Itabuna and Porto Seguro, all considered hotspots for HTLV infection, despite HTLV and HCV being widespread throughout the state. It is our hope that these findings will provide support for the implementation of preventive measures against the spread of these viruses, especially in areas where higher rates of HTLV/HCV coinfection were described. Moreover, as the presence of HTLV can negatively impact the course of HCV infection, the surveillance of active cases should be a priority in order to provide early treatment. The identification, control and prevention of the main risk factors associated with HTLV/HCV coinfection can lead to efficacious actions in a variety of epidemiological contexts specific to each affected region.

Supporting information

S1 Table. Anonymized data set comprised of HTLV and HCV tested individuals living in Bahia, Brazil from 2004 to 2013.

(XLSX)

Click here for additional data file. (11.1MB, xlsx)

Acknowledgments

We thank Andris K. Walter for providing English language revision and manuscript copyediting assistance.

Data Availability

All relevant data are within the manuscript and its Supporting Information files.

Funding Statement

This work was supported by the Coordination of Superior Level Staff Improvement-Brazil (CAPES) - Finance Code 001 and National Foundation for the Development of Private Higher Education (FUNADESP), grants 9600140 and 9600141. Maria Fernanda R. Grassi and Bernardo Galvão-Castro are research fellows of CNPq (process no. 304811/2017-3 and 311054/2014-5, respectively).

References

  • 1.Sullivan MT, Williams AE, Fang CT, Grandinetti T, Poiesz BJ, Ehrlich GD. Transmission of human T-lymphotropic virus types I and II by blood transfusion. A retrospective study of recipients of blood components (1983 through 1988). The American Red Cross HTLV-I/II Collaborative Study Group. Arch Intern Med. 1991; 151: 2043–2048. 10.1001/archinte.1991.00400100115019 . [DOI] [PubMed] [Google Scholar]
  • 2.Manns A, Wilks RJ, Murphy EL, Haynes G, Figueroa JP, Barnett M, et al. A prospective study of transmission by transfusion of HTLV-I and risk factors associated with seroconversion. Int J Cancer. 1992; 51: 886–891. 10.1002/ijc.2910510609 . [DOI] [PubMed] [Google Scholar]
  • 3.Alter MJ. Prevention of spread of hepatitis C. Hepatology. 2002; 36: S93–S98. 10.1053/jhep.2002.36389 . [DOI] [PubMed] [Google Scholar]
  • 4.Nunes D, Boa-Sorte N, Grassi MF, Taylor GP, Teixeira MG, Barreto ML, et al. HTLV-1 is predominantly sexually transmitted in Salvador, the city with the highest HTLV-1 prevalence in Brazil. PLoS One. 2017; 12:e0171303 10.1371/journal.pone.0171303 . [DOI] [PMC free article] [PubMed] [Google Scholar]
  • 5.Bittencourt AL, Dourado I, Filho PB, Santos M, Valadao E, Alcantara LC, et al. Human T-cell lymphotropic virus type 1 infection among pregnant women in northeastern Brazil. J Acquir Immune Defic Syndr. 2001; 26: 490–494. 10.1097/00126334-200104150-00016 . [DOI] [PubMed] [Google Scholar]
  • 6.Li HC, Biggar RJ, Miley WJ, Maloney EM, Cranston B, Hanchard B, et al. Provirus load in breast milk and risk of mother-to-child transmission of human T lymphotropic virus type I. J Infect Dis. 2004; 190: 1275–1278. Epub 2004 Aug 30. 10.1086/423941 . [DOI] [PubMed] [Google Scholar]
  • 7.Gessain A, Cassar O. Epidemiological aspects and world distribution of HTLV-1 infection. Front Microbiol. 2012; 3: 388 10.3389/fmicb.2012.00388 . [DOI] [PMC free article] [PubMed] [Google Scholar]
  • 8.Catalan-Soares B, Carneiro-Proietti AB, Proietti FA, Interdisciplinary HRG. Heterogeneous geographic distribution of human T-cell lymphotropic viruses I and II (HTLV-I/II): serological screening prevalence rates in blood donors from large urban areas in Brazil. Cad Saude Publica. 2005; 21: 926–931. Epub 2005 May 2. 10.1590/s0102-311x2005000300027 . [DOI] [PubMed] [Google Scholar]
  • 9.Pereira FM, Almeida MC, Santos FL, Carreiro RP, Regis-Silva CG, Galvão-Castro B, et al. Evidence of new highly endemic clusters of human T-cell lymphotropic viral infection (HTLV) in Bahia, Brazil. Front Microbiol. 2019; 10: 1002 10.3389/fmicb.2019.01002 . [DOI] [PMC free article] [PubMed] [Google Scholar]
  • 10.Pereira LM, Martelli CM, Moreira RC, Merchan-Hamman E, Stein AT, Cardoso MR, et al. Prevalence and risk factors of Hepatitis C virus infection in Brazil, 2005 through 2009: a cross-sectional study. BMC Infect Dis. 2013; 13: 60 10.1186/1471-2334-13-60 . [DOI] [PMC free article] [PubMed] [Google Scholar]
  • 11.Zarife MA, Silva LK, Silva MB, Lopes GB, Barreto ML, Teixeira Mda G, et al. Prevalence of hepatitis C virus infection in north-eastern Brazil: a population-based study. Trans R Soc Trop Med Hyg. 2006; 100: 663–668. Epub 2005 Dec 28. 10.1016/j.trstmh.2005.09.009 . [DOI] [PubMed] [Google Scholar]
  • 12.Nakashima K, Hayashi J, Hirata M, Kashiwagi S, Eda F. Hepatitis C virus infection on Iki Island, Japan, an area endemic for human T-lymphotropic virus type-I. A preliminary study in patients at clinics or hospitals. J Epidemiol. 1994; 4: 17–23. 10.2188/jea.4.17. [DOI] [Google Scholar]
  • 13.Ziaee M, Namaei MH, Azarkar G. The prevalence of HTLV-1 and its co-Infection with HCV, HBV and HIV in hemophilic patients. Pak J Med Sci. 2015; 31: 1246–1249. 10.12669/pjms.315.7888 . [DOI] [PMC free article] [PubMed] [Google Scholar]
  • 14.Prasetyo AA, Dirgahayu P, Sari Y, Hudiyono H, Kageyama S. Molecular epidemiology of HIV, HBV, HCV, and HTLV-1/2 in drug abuser inmates in central Javan prisons, Indonesia. J Infect Dev Ctries. 2013; 7: 453–467. 10.3855/jidc.2965 . [DOI] [PubMed] [Google Scholar]
  • 15.Boschi-Pinto C, Stuver S, Okayama A, Trichopoulos D, Orav EJ, Tsubouchi H, et al. A follow-up study of morbidity and mortality associated with hepatitis C virus infection and its interaction with human T lymphotropic virus type I in Miyazaki, Japan. J Infect Dis. 2000; 181: 35–41. 10.1086/315177 . [DOI] [PubMed] [Google Scholar]
  • 16.Ramos JM, Belda S, Reyes F, Rodriguez JC, Royo G, Gutierrez F. Prevalence of HIV, HBV, HCV, HTLV and Treponema pallidum among patients attending a rural hospital in Southern Ethiopia. J Clin Virol. 2012; 53: 268–269. Epub 2011 Dec 30. 10.1016/j.jcv.2011.12.004 . [DOI] [PubMed] [Google Scholar]
  • 17.Vallejo A, Loza E, Mateos M. Absence of HTLV-1/2 infection among HCV- infected patients with no HIV-1/2 infection in Spain. J Clin Virol. 2015; 64: 72–73. Epub 2015 Jan 14. 10.1016/j.jcv.2015.01.010 . [DOI] [PubMed] [Google Scholar]
  • 18.Kucharska M, Inglot M, Szymczak A, Rymer W, Zalewska M, Malyszczak K, et al. Co-infection of the hepatitis C virus with other blood-borne and hepatotropic viruses among hemophilia patients in Poland. Hepat Mon. 2016; 16: e35658 10.5812/hepatmon.35658 . [DOI] [PMC free article] [PubMed] [Google Scholar]
  • 19.de la Fuente L, Toro C, Soriano V, Brugal MT, Vallejo F, Barrio G, et al. HTLV infection among young injection and non-injection heroin users in Spain: prevalence and correlates. J Clin Virol. 2006; 35: 244–249. Epub 2005 Sep 6. 10.1016/j.jcv.2005.06.006 . [DOI] [PubMed] [Google Scholar]
  • 20.Caterino-de-Araujo A, Alves FA, Campos KR, Lemos MF, Moreira RC. Making the invisible visible: searching for human T-cell lymphotropic virus types 1 and 2 (HTLV-1 and HTLV-2) in Brazilian patients with viral hepatitis B and C. Mem Inst Oswaldo Cruz. 2018; 113: 130–134. 10.1590/0074-02760170307 . [DOI] [PMC free article] [PubMed] [Google Scholar]
  • 21.Maciel AM, Mello CE. Hepatitis C virus and Human T-cell lymphotropic virus co- infection: an epidemiological, clinical and laboratory analysis. Arch Clin Microbiol. 2015; 6: 1–7. [Google Scholar]
  • 22.Pinto MT, Rodrigues ES, Malta TM, Azevedo R, Takayanagui OM, Valente VB, et al. HTLV-1/2 seroprevalence and coinfection rate in Brazilian first-time blood donors: an 11-year follow-up. Rev Inst Med Trop Sao Paulo. 2012; 54: 123–129. 10.1590/s0036-46652012000300002 . [DOI] [PubMed] [Google Scholar]
  • 23.Bahia F, Novais V, Evans J, Le Marchand C, Netto E, Page K, et al. The impact of human T-cell lymphotropic virus I infection on clinical and immunologic outcomes in patients coinfected with HIV and hepatitis C virus. J Acquir Immune Defic Syndr. 2011; 57: S202–S207. 10.1097/QAI.0b013e31821e9a1e . [DOI] [PMC free article] [PubMed] [Google Scholar]
  • 24.Abad-Fernández M, Moreno A, Dronda F, del Campo S, Quereda C, Casado JL, et al. Delayed liver fibrosis in HTLV-2-infected patients co-infected with HIV-1 and hepatitis C virus with suppressive antiretroviral therapy. AIDS. 2015; 29: 401–409. 10.1097/QAD.0000000000000555 . [DOI] [PubMed] [Google Scholar]
  • 25.Silva MC, Silva CA, Machado GU, Atta A, S MF, Carvalho E, et al. HCV/HTLV coinfection: Does HTLV-1 interfere in the natural history of HCV-related diseases? J Med Virol. 2016; 88: 1967–1972. Epub 2016 Apr 22. 10.1002/jmv.24538 . [DOI] [PubMed] [Google Scholar]
  • 26.Espíndola OM, Vizzoni AG, Lampe E, Andrada-Serpa MJ, Araujo AQ, Leite AC. Hepatitis C virus and human T-cell lymphotropic virus type 1 co-infection: impact on liver disease, virological markers, and neurological outcomes. Int J Infect Dis. 2017; 57: 116–122. Epub 2017 Feb 7. 10.1016/j.ijid.2017.01.037 . [DOI] [PubMed] [Google Scholar]
  • 27.Kamihira S, Momita S, Ikeda S, Yamada Y, Sohda H, Atogami S, et al. Cohort study of hepatotropic virus and human T lymphotropic virus type-I infections in an area endemic for adult T cell leukemia. Jpn J Med. 1991; 30: 492–497. 10.2169/internalmedicine1962.30.492 . [DOI] [PubMed] [Google Scholar]
  • 28.Kishihara Y, Furusyo N, Kashiwagi K, Mitsutake A, Kashiwagi S, Hayashi J. Human T lymphotropic virus type 1 infection influences hepatitis C virus clearance. J Infect Dis. 2001; 184: 1114–1119. Epub 2001 Sep 21. 10.1086/323890 . [DOI] [PubMed] [Google Scholar]
  • 29.Hisada M, Chatterjee N, Zhang M, Battjes RJ, Goedert JJ. Increased hepatitis C virus load among injection drug users infected with human immunodeficiency virus and human T lymphotropic virus type II. J Infect Dis. 2003; 188: 891–897. Epub 2003 Sep 9. 10.1086/377585 . [DOI] [PubMed] [Google Scholar]
  • 30.Tokunaga M, Uto H, Oda K, Tokunaga M, Mawatari S, Kumagai K, et al. Influence of human T-lymphotropic virus type 1 coinfection on the development of hepatocellular carcinoma in patients with hepatitis C virus infection. J Gastroenterol. 2014; 49: 1567–1577. Epub 2014 Jan 25. 10.1007/s00535-013-0928-5 . [DOI] [PubMed] [Google Scholar]
  • 31.Dourado I, Alcantara LC, Barreto ML, da Gloria Teixeira M, Galvão-Castro B. HTLV-I in the general population of Salvador, Brazil: a city with African ethnic and sociodemographic characteristics. J Acquir Immune Defic Syndr. 2003; 34: 527–531. 10.1097/00126334-200312150-00013 . [DOI] [PubMed] [Google Scholar]
  • 32.Brito V da S, Santos FLN, Gonçalves NLS, Araujo TH, Nascimento DSV, Pereira FM, et al. Performance of commercially available serological screening tests for human T-cell lymphotropic virus infection in Brazil. J Clin Microbiol. 2018; pii: e00961–18. 10.1128/JCM.00961-18 . [DOI] [PMC free article] [PubMed] [Google Scholar]
  • 33.Naz A, Mukry SN, Naseer I, Shamsi TS. Evaluation of efficacy of serological methods for detection of HCV infection in blood donors: A single centre experience. Pakistan J Med Sci. 2018; 34: 1204–1208. 10.12669/pjms.345.15707 . [DOI] [PMC free article] [PubMed] [Google Scholar]
  • 34.Moreira M, Ramos A, Netto EM, Brites C. Characteristics of co-infections by HCV and HBV among Brazilian patients infected by HIV-1 and/or HTLV-1. Braz J Infect Dis. 2013; 17: 661–666. Epub 2013 Sep 9. 10.1016/j.bjid.2013.04.009 . [DOI] [PMC free article] [PubMed] [Google Scholar]
  • 35.Milagres FA, Duarte MI, Viso AT, Segurado AC. Hepatitis C virus and human T-lymphotropic virus coinfection: epidemiological, clinical, laboratory and histopathological features. Rev Soc Bras Med Trop. 2009; 42: 363–368. 10.1590/s0037-86822009000400001 . [DOI] [PubMed] [Google Scholar]
  • 36.Prati D. Transmission of hepatitis C virus by blood transfusions and other medical procedures: a global review. J Hepatol. 2006; 45: 607–616. Epub 2006 Jul 25. 10.1016/j.jhep.2006.07.003 . [DOI] [PubMed] [Google Scholar]
  • 37.Caterino-de-Araujo A, Sacchi CT, Goncalves MG, Campos KR, Magri MC, Alencar WK, et al. Short Communication: current prevalence and risk factors associated with human T lymphotropic virus type 1 and human T lymphotropic virus type 2 infections among HIV/AIDS patients in São Paulo, Brazil. AIDS Res Hum Retroviruses. 2015; 31: 543–549. Epub 2015 Jan 2. 10.1089/AID.2014.0287 . [DOI] [PMC free article] [PubMed] [Google Scholar]
  • 38.Oliveira-Filho AB, Sawada L, Pinto LC, Locks D, Bahia SL, Castro JA, et al. Epidemiological aspects of HCV infection in non-injecting drug users in the Brazilian state of Para, eastern Amazon. Virol J. 2014; 11: 38 10.1186/1743-422X-11-38 . [DOI] [PMC free article] [PubMed] [Google Scholar]
  • 39.Alter M. Epidemiology of hepatitis C virus infection. World J Gastroenterol. 2007; 13: 2436–2441. 10.3748/wjg.v13.i17.2436 . [DOI] [PMC free article] [PubMed] [Google Scholar]
  • 40.Cardoso DF, Souza FV, Fonseca LA, Duarte AJ, Casseb J. Influence of human T-cell lymphotropic virus type 1 (HTLV-1) Infection on laboratory parameters of patients with chronic hepatitis C virus. Rev Inst Med Trop São Paulo. 2009; 51: 325–329. 10.1590/s0036-46652009000600003 . [DOI] [PubMed] [Google Scholar]
  • 41.Terrault NA. Sexual activity as a risk factor for hepatitis C. Hepatology. 2002; 36: S99–S105. 10.1053/jhep.2002.36797 . [DOI] [PubMed] [Google Scholar]
  • 42.Ishak R, Harrington WJ Jr., Azevedo VN, Eiraku N, Ishak MO, Guerreiro JF, et al. Identification of human T cell lymphotropic virus type IIa infection in the Kayapo, an indigenous population of Brazil. AIDS Res Hum Retroviruses. 1995; 11: 813–821. 10.1089/aid.1995.11.813 . [DOI] [PubMed] [Google Scholar]
  • 43.Le Marchand C, Bahia F, Page K, Brites C. Hepatitis C virus infection and spontaneous clearance in HTLV-1 and HIV co-infected patients in Salvador, Bahia, Brazil. Braz J Infect Dis. 2015; 19: 486–491. Epub 2015 Aug 5. 10.1016/j.bjid.2015.06.007 . [DOI] [PMC free article] [PubMed] [Google Scholar]
  • 44.Ministério da Saúde do Brasil. Boletim Epidemiológico—Hepatites virais. Brasília: Ministério da Saúde; 2018. Available: http://www.aids.gov.br.
  • 45.Messina JP, Humphreys I, Flaxman A, Brown A, Cooke GS, Pybus OG, et al. Global distribution and prevalence of hepatitis C virus genotypes. Hepatology. 2015; 61: 77–87. Epub 2014 Jul 28 10.1002/hep.27259 . [DOI] [PMC free article] [PubMed] [Google Scholar]
  • 46.Petruzziello A, Marigliano S, Loquercio G, Cacciapuoti C. Hepatitis C virus (HCV) genotypes distribution: an epidemiological up-date in Europe. Infect Agent Cancer. 2016; 11: 53 10.1186/s13027-016-0099-0 . [DOI] [PMC free article] [PubMed] [Google Scholar]

Decision Letter 0

William M Switzer

16 Oct 2019

PONE-D-19-25685

Distribution of Human T-Lymphotropic Virus (HTLV) and Hepatitis C Co-infection in Bahia, Brazil,

PLOS ONE

Dear Dr. Santos,

Thank you for submitting your manuscript to PLOS ONE. After careful consideration, we feel that it has merit but does not fully meet PLOS ONE’s publication criteria as it currently stands. Therefore, we invite you to submit a revised version of the manuscript that addresses the points raised during the review process.

Both expert reviewers found several areas of the manuscript that require revision. Please provide a revised manuscript that addresses all comments and suggestions of both reviewers. For the HTLV and HCV serology, please include an explanation of the differences in assay sensitivity and specificity for the two different serological assays used for each virus and how that may have impacted the study results.

We would appreciate receiving your revised manuscript by Nov 30 2019 11:59PM. When you are ready to submit your revision, log on to https://www.editorialmanager.com/pone/ and select the 'Submissions Needing Revision' folder to locate your manuscript file.

If you would like to make changes to your financial disclosure, please include your updated statement in your cover letter.

To enhance the reproducibility of your results, we recommend that if applicable you deposit your laboratory protocols in protocols.io, where a protocol can be assigned its own identifier (DOI) such that it can be cited independently in the future. For instructions see: http://journals.plos.org/plosone/s/submission-guidelines#loc-laboratory-protocols

Please include the following items when submitting your revised manuscript:

  • A rebuttal letter that responds to each point raised by the academic editor and reviewer(s). This letter should be uploaded as separate file and labeled 'Response to Reviewers'.

  • A marked-up copy of your manuscript that highlights changes made to the original version. This file should be uploaded as separate file and labeled 'Revised Manuscript with Track Changes'.

  • An unmarked version of your revised paper without tracked changes. This file should be uploaded as separate file and labeled 'Manuscript'.

Please note while forming your response, if your article is accepted, you may have the opportunity to make the peer review history publicly available. The record will include editor decision letters (with reviews) and your responses to reviewer comments. If eligible, we will contact you to opt in or out.

We look forward to receiving your revised manuscript.

Kind regards,

William M. Switzer, MPH

Academic Editor

PLOS ONE

Journal Requirements:

When submitting your revision, we need you to address these additional requirements.

1. Please ensure that your manuscript meets PLOS ONE's style requirements, including those for file naming. The PLOS ONE style templates can be found at http://www.journals.plos.org/plosone/s/file?id=wjVg/PLOSOne_formatting_sample_main_body.pdf and http://www.journals.plos.org/plosone/s/file?id=ba62/PLOSOne_formatting_sample_title_authors_affiliations.pdf

2. In ethics statement in the manuscript and in the online submission form, please provide additional information about the patient records/samples used in your retrospective study. Specifically, please ensure that you have discussed whether all data/samples were fully anonymized before you accessed them and/or whether the IRB or ethics committee waived the requirement for informed consent. If patients provided informed written consent to have data/samples from their medical records used in research, please include this information.

3. Thank you for stating the following financial disclosure:

'The funders had no role in study design, data collection and analysis, decision to

publish, or preparation of the manuscript.'

  1. Please provide an amended Funding Statement that declares *all* the funding or sources of support received during this specific study (whether external or internal to your organization) as detailed online in our guide for authors at http://journals.plos.org/plosone/s/submit-now.  

  2. Please state what role the funders took in the study.  If any authors received a salary from any of your funders, please state which authors and which funder. If the funders had no role, please state: "The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript."

Please include your amended statements within your cover letter; we will change the online submission form on your behalf.

Additional Editor Comments (if provided):

[Note: HTML markup is below. Please do not edit.]

Reviewers' comments:

Reviewer's Responses to Questions

Comments to the Author

1. Is the manuscript technically sound, and do the data support the conclusions?

The manuscript must describe a technically sound piece of scientific research with data that supports the conclusions. Experiments must have been conducted rigorously, with appropriate controls, replication, and sample sizes. The conclusions must be drawn appropriately based on the data presented.

Reviewer #1: Partly

Reviewer #2: No

**********

2. Has the statistical analysis been performed appropriately and rigorously?

Reviewer #1: I Don't Know

Reviewer #2: No

**********

3. Have the authors made all data underlying the findings in their manuscript fully available?

The PLOS Data policy requires authors to make all data underlying the findings described in their manuscript fully available without restriction, with rare exception (please refer to the Data Availability Statement in the manuscript PDF file). The data should be provided as part of the manuscript or its supporting information, or deposited to a public repository. For example, in addition to summary statistics, the data points behind means, medians and variance measures should be available. If there are restrictions on publicly sharing data—e.g. participant privacy or use of data from a third party—those must be specified.

Reviewer #1: Yes

Reviewer #2: Yes

**********

4. Is the manuscript presented in an intelligible fashion and written in standard English?

PLOS ONE does not copyedit accepted manuscripts, so the language in submitted articles must be clear, correct, and unambiguous. Any typographical or grammatical errors should be corrected at revision, so please note any specific errors here.

Reviewer #1: Yes

Reviewer #2: Yes

**********

5. Review Comments to the Author

Please use the space provided to explain your answers to the questions above. You may also include additional comments for the author, including concerns about dual publication, research ethics, or publication ethics. (Please upload your review as an attachment if it exceeds 20,000 characters)

Reviewer #1: PONE-D-19-25685

Distribution of Human T-Lymphotropic Virus (HTLV) and Hepatitis C Co-infection in Bahia, Brazil

The manuscript contains novel information about HTLV/HCV coinfection and prevalence in Bahia and is based on very large cohort, covering approx. 0.8% of the state’s population.

Comments:

1. Please, include in the introduction why is the co-infection rate of those two agents important -clinical outcomes, treatment strategies, epidemiology, or not known at all? There is some information about this in the discussion, but it needs to be in the introduction to better justify the undertaking of the work. Lines 71-72 would be a good place to include such text.

2. Please, include in the description of the study design what was the no-random sampling bias that lead to testing predominantly females.

3. It is not clear from the data shown in the tables and figures why is co-infection more frequent in males at median age of 59? Please, demonstrate this conclusion with the specific results and support it with significance values.

4. Please, mention the genotyping method for HCV in the methods and explain why so few (only 30%) were successfully genotyped.

Reviewer #2: This manuscript aims to report on the prevalence of co-infection with both HCV and HTLV infection in the state of Bahia, Brazil, an area where HTLV is highly prevalent. The authors use a valuable data source from a central lab reporting source and analyses are generally well described and conducted. However, there are numerous issues that need to be addressed that would make this article have more public health and clinical impact. Why is mapping this important?

1) Throughout the manuscript the authors present different estimates of prevalence of co-infection: (a) in the general population; (b) prevalence of HTLV given HCV infection (i.e. the denominator is HCV infected) and (c) prevalence of HCV given HTLV infection. These all have different denominators, interpretations and epidemiological significance. They cannot be compared, yet the authors do this. For example, the paragraph that starts on line 66 this - what are the authors comparing and what is it they are focused on? is it overall HCV/HTLV in the whole population? or one given the other, and if so which? This needs to be reconciled throughout the manuscript for studies cited and for the results. Then the conclusions can be better articulated and interpreted. Note that the Discussion also conflated these different approaches and the interpretation is flawed as a result. (eg, the paragraph starting on line 177: we don't know what the denominator is for the Sao Paulo study and then this is compared to Japan where author present the prevalence of HCV given HTLV infection).

2) The authors have not presented the main rationale for the study - why is this analysis important to public health and or clinical practice? What gap does this analysis fill and how should it be used to improve health or change policy?

3) It would be very very good to know how the sample of people who were tested for BOTH viruses (which is the sample correct?) compare to the general population? it is hard to interpret this from what is presented. The authors state that because it is a large sample and it is noted that females are over-represented. I am assuming this is due to prenatal testing, but the authors should explain why this is. Several areas are 100% female samples. Then this needs to be better addressed in the limitations. The manuscript needs a table with demographics and primary outcome (HCV+HTLV exposure)

4) A major limitation is that the authors are presenting prevalence of EXPOSURE to HCV - as they only present anti-HCV results. Unlike HTLV, HCV infection can be spontaneously cleared and treated. Thus this estimate does not reflect prevalence of infection, but prevalence of exposure. If authors had HCV RNA results this would be better to use for the prevalence of co-infection estimate.

5) The low number of genotyped samples presents large interpretation issues: one because obviously only RNA positive samples can be genotyped, and there are potential biases resulting from (i) differential clearance rates of HCV found in HTLV-HCV infected persons, and (ii) potential differential clearance by genotype. This needs to be addressed in limitations.

Minor comments:

1) Introduction: (a) line 62: specify that this is one study conducted in rural Ethiopia. If possible let reader know if urban Ethiopia has higher co-prevalence; (b) line 65 - the conclusion of the study in Spain regarding people who inject drugs; - did this study have any data on country of origin? in particular African origin?

2) If you don't have HCV RNA results, then the manuscript needs to specify that this is HCV exposure and not HCV infection.

3) The Discussion needs to directly address how this data contributes to practice and or policy.

**********

6. PLOS authors have the option to publish the peer review history of their article (what does this mean?). If published, this will include your full peer review and any attached files.

If you choose “no”, your identity will remain anonymous but your review may still be made public.

Do you want your identity to be public for this peer review? For information about this choice, including consent withdrawal, please see our Privacy Policy.

Reviewer #1: No

Reviewer #2: No

[NOTE: If reviewer comments were submitted as an attachment file, they will be attached to this email and accessible via the submission site. Please log into your account, locate the manuscript record, and check for the action link "View Attachments". If this link does not appear, there are no attachment files to be viewed.]

While revising your submission, please upload your figure files to the Preflight Analysis and Conversion Engine (PACE) digital diagnostic tool, https://pacev2.apexcovantage.com/. PACE helps ensure that figures meet PLOS requirements. To use PACE, you must first register as a user. Registration is free. Then, login and navigate to the UPLOAD tab, where you will find detailed instructions on how to use the tool. If you encounter any issues or have any questions when using PACE, please email us at figures@plos.org. Please note that Supporting Information files do not need this step.

PLoS One. 2020 Jul 21;15(7):e0223087. doi: 10.1371/journal.pone.0223087.r002

Author response to Decision Letter 0

16 Mar 2020

Dear Editor,

The response to the questions are below (PONE-D-19-25685). Additionally, we have included statements in the Ethics statement, Funding and Competing interests sections, as requested by Plos One Staff:

Ethics statement

Before: The Institutional Review Board (IRB) for Human Research at the Gonçalo Moniz Institute of the Oswaldo Cruz Foundation (Salvador, Bahia, Brazil) provided ethical approval to conduct this study (CAAE number 22478813.7.0000.0040).

After (line 84-88): The Institutional Review Board (IRB) for Human Research at the Gonçalo Moniz Institute of the Oswaldo Cruz Foundation (Salvador, Bahia, Brazil) provided ethical approval to conduct this study (CAAE number 22478813.7.0000.0040). In order to maintain patient information confidentiality, data were fully were anonymized so that the researchers do not have access to patient’s individual information avoiding the need for verbal or written consent.

Funding

Before: No text.

After (line 285-287): “The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.”

Competing interests

Before: No text.

After (line 288-290): “The authors have declared that no competing interests exist.”

Editor: PONE-D-19-25685

Question 1 - Editor. Both expert reviewers found several areas of the manuscript that require revision. Please provide a revised manuscript that addresses all comments and suggestions of both reviewers. For the HTLV and HCV serology, please include an explanation of the differences in assay sensitivity and specificity for the two different serological assays used for each virus and how that may have impacted the study results.

Reply: We have included into the discussion section of the manuscript the following statement:

Before: No text.

After (line 216-223): “Throughout the study period, the testing methodology for both HTLV and HCV was updated from ELISA to chemiluminescence assays. Nonetheless, both tests offer similarly high sensitivity and specificity. Recent studies evaluating the performance of these methods indicate improved accuracy using chemiluminescence, both in HTLV [32] and HCV serology [33], i.e. both can be effectively used for serological screening in the laboratory diagnosis of HTLV and HCV. Chemiluminescence is mainly used by the laboratories that analyze a large number of samples, as this technique reduces time needed to produce results and minimizes errors in analysis.”

New references have been added to support the statements above:

(line 405-408): 32. Brito V da S, Santos FLN, Gonçalves NLS, Araujo TH, Nascimento DSV, Pereira FM, et al. Performance of commercially available serological screening tests for human T-cell lymphotropic virus infection in Brazil. J Clin Microbiol. 2018; pii: e00961-18. https://doi:10.1128/JCM.00961-18 PMID: 30232131.

(line 409-412): 33. Naz A, Mukry SN, Naseer I, Shamsi TS. Evaluation of efficacy of serological methods for detection of HCV infection in blood donors: A single centre experience. Pakistan J Med Sci. 2018; 34: 1204-1208. https://doi:10.12669/pjms.345.15707 PMID: 30344577.

Reviewer #1: PONE-D-19-25685

Question 1 - Reviewer 1. Please, include in the introduction why is the co-infection rate of those two agents important -clinical outcomes, treatment strategies, epidemiology, or not known at all? There is some information about this in the discussion, but it needs to be in the introduction to better justify the undertaking of the work. Lines 71-72 would be a good place to include such text.

Reply: We concur entirely with the reviewer with respect to the inclusion of further information regarding clinical outcomes, treatment strategies and the epidemiology of co-infection between HTLV and HCV agents. We have modified this section of the introduction to incorporate the reviewer’s suggestion.

Before: “Brazil is endemic for both HTLV and HCV, and the presence of coinfection has been reported in several populations, especially those in Southeastern Brazil. The prevalence of HTLV in individuals infected with HCV ranges from 5.3% in São Paulo (20) to 7.5% in Rio de Janeiro (21). In addition, in blood donors, HCV was found in 35.9% of first-time HTLV-positive blood donors (22) and 1.5% in HTLV-positive men who have sex with men (23).

In light of considerations regarding the influence of HTLV/HCV coinfection on the outcome of either infection, the present study aimed to determine the rate of coinfection throughout the state of Bahia and map the geographical distribution of cases over a 10-year period.”

After (line 66-80): “…Brazil is endemic for both HTLV and HCV, and the presence of coinfection has been rarely reported in HCV patients undergoing treatment, as well as in blood donors, especially those in Southeastern Brazil. The prevalence of HTLV in individuals infected with HCV ranges from 5.3% in São Paulo [20] to 7.5% in Rio de Janeiro [21]. In addition, in blood donors, HCV was found in 35.9% of first-time HTLV-positive blood donors [22].

Contradictory clinical outcomes in the course of HTLV/HCV coinfection have been reported in Brazil and Japan. A better prognosis was described in coinfected Brazilian individuals who presented higher levels of Th1-type cytokines and CD4+ T lymphocytes, as well as lower hepatic fibrosis and alanine aminotransferase (ALT) [23–26]. Conversely, a Japanese study involving coinfected individuals described higher viral loads, a more rapid progression to hepatocellular carcinoma and a decreased response to treatment with interferon [15,27–30]. In light of considerations regarding the influence of HTLV/HCV coinfection on the outcome of either infection and a lack of epidemiologic studies, notably in the Brazilian Northeast macroregion, the present study aimed to determine the rate of coinfection throughout the state of Bahia and map the geographical distribution of cases over a 10-year period.”

New references have been added to support the statements above:

(line 372-375): 24. Abad-Fernández M, Moreno A, Dronda F, del Campo S, Quereda C, Casado JL, et al. Delayed liver fibrosis in HTLV-2-infected patients co-infected with HIV-1 and hepatitis C virus with suppressive antiretroviral therapy. AIDS. 2015; 29: 401-409. https://doi:10.1097/QAD.0000000000000555. PMID: 25565497.

(line 385-388): 27. Kamihira S, Momita S, Ikeda S, Yamada Y, Sohda H, Atogami S, et al. Cohort study of hepatotropic virus and human T lymphotropic virus type-I infections in an area endemic for adult T cell leukemia. Jpn J Med. 1991; 30: 492-497. https://doi:10.2169/internalmedicine1962.30.492. PMID: 1665877.

(line 389-392): 28. Kishihara Y, Furusyo N, Kashiwagi K, Mitsutake A, Kashiwagi S, Hayashi J. Human T lymphotropic virus type 1 infection influences hepatitis C virus clearance. J Infect Dis. 2001; 184: 1114-1119. Epub 2001 Sep 21. https://doi:10.1086/323890. PMID: 11598833.

(line 397-400): 30. Tokunaga M, Uto H, Oda K, Tokunaga M, Mawatari S, Kumagai K, et al. Influence of human T-lymphotropic virus type 1 coinfection on the development of hepatocellular carcinoma in patients with hepatitis C virus infection. J Gastroenterol. 2014; 49: 1567-1577. Epub 2014 Jan 25. https://doi:10.1007/s00535-013-0928-5 PMID: 24463696.

Question 2 - Reviewer 1. Please, include in the description of the study design what was the no-random sampling bias that lead to testing predominantly females.

Reply: We have modified “Material and Methods” and “Discussion” sections in the manuscript to incorporate the reviewer’s suggestions

Material and Methods section:

Before:

“Study design The present retrospective study was performed in the state of Bahia, Brazil, the fourth largest state in terms of population size (15,203,934 inhabitants), and the fifth largest in terms of area: 564.722,611 km2. Bahia is comprised of 417 municipalities, which are grouped into 32 microregions and seven mesoregions according to economic and social similarities by the Brazilian National Institute of Geography and Statistics (IBGE) (http://www.ibge.gov.br). Data were obtained from the Central Laboratory of Public Health of Bahia (LACEN-BA), which is responsible for the laboratory analysis of infectious disease surveillance throughout the state. Individuals were included if submitted to serological testing for both HTLV and HCV, either concomitantly or in isolation, between 2004 to 2013. Any indeterminate confirmatory test results were excluded from the present analysis.”

After (lines 87-101): “Study area The study was carried out in the state of Bahia, Brazil, the fourth largest state in terms of population size (15,203,934 inhabitants), and the fifth-largest in terms of area: 564.722,611 km2. Bahia is comprised of 417 municipalities, which are grouped into 32 microregions and seven mesoregions according to economic and social similarities by the Brazilian National Institute of Geography and Statistics (IBGE) (http://www.ibge.gov.br).

Study design The present ecological retrospective study was performed using data obtained from the Central Laboratory of Public Health of Bahia (LACEN-BA), which is responsible for the laboratory analysis of infectious disease surveillance throughout the state. The population served by LACEN mainly consists of individuals who exhibit symptoms of infectious disease, pregnant women and individuals referred by blood blanks, the prison system or public health units distributed throughout the state of Bahia. Individuals were included if submitted to serological testing for both HTLV and HCV, either concomitantly or in isolation, between 2004 to 2013. Any indeterminate confirmatory test results were excluded from the present analysis.

Discussion section:

Before: “The main limitation of the present study was the use of non-random sampling, which resulted in a predominance of females. However, the robust representation of cases reported throughout the state’s municipalities, as well as the absolute number of individuals analyzed, provide an overview of the circulation of HTLV and HCV in the state.”

After (line 258-2631): “The main limitation of the present study was the use of non-random sampling, which resulted in a predominance of females. In the state of Bahia, serological HTLV screening for pregnant women is compulsory since 2011, which could thusly contribute to a higher proportion of women in the samples analyzed. However, the robust representation of cases reported throughout the state’s municipalities, as well as the absolute number of individuals analyzed, provide an overview of the circulation of HTLV and HCV in the state.”

Question 3 - Reviewer 1. It is not clear from the date shown in the tables and figures why is co-infection more frequent in males at middle age of 59? Please demonstrate this conclusion with the specific results and support it with significance values.

Reply: The reviewer raises a valid point. In order to clarify this data in the manuscript, we have included the median age instead of simply reporting frequency. It is important to note that our analysis was conducted using a convenience sampling (i.e. not probabilistic).

Before: “With regard to coinfection, HCV infection was detected mainly among HTLV-2 (37.9%) infected individuals, followed by HTLV-1 (13.3%) and HTLV-1/2 (11.6%). Coinfection was more frequent among males (51%, 52/101), with a median age of 59 years [interquartile range (IQR): 46 - 59 years].”

After (line 146-152): “With regard to coinfection, HCV infection was detected mainly among HTLV-2 (37.9%) infected individuals, followed by HTLV-1 (13.3%) and HTLV-1/2 (11.6%). The HTLV infection prevalence in the 120,192 individuals submitted to both anti-HCV and anti-HTLV-1/2 was substantially higher in women than in man subjects (75.6% vs. 24.4%, p < 0.001). The coinfection rate was more frequent in men (~30%, 52/174; p< 0.0001) compared to women (~9%, 49/534). The median age of cases de HTLV/HCV was 59 years [interquartile range (IQR): 46 - 59 years].”

Question 4 - Reviewer 1. Please, mention the genotyping method for HCV in the methods and explain why so few (only 30%) were successfully genotyped.

Reply: We have included in the methods section the genotyping method for HCV:

Before: No text.

After (line 111-117): “With respect to molecular testing, RT-PCR (AMPLICOR MONITOR®, Roche Molecular Systems, Branchburg, NJ, USA) was employed in accordance with the manufacturer's specifications. Genotyping was performed by analyzing the highly conserved 5’ untranslated region using the Linear Array Hepatitis C Virus Genotyping Test (LiPA - Line Probe Assay - Roche Diagnostics, USA), following the manufacturer’s guidelines. This assay allows for the determination of six genotypes and subtypes (1a, 1b, 2, 2a, 2b, 3, 3a, 4, 4c, 5, 5a and 6).”

In fact, only 30% of samples were successfully genotyped since this is a retrospective evaluation that considers a 10-year period (2004-2013). The database was generated from the records of a laboratory surveillance service that were sometimes lacking pertinent data. We have included in the discussion section the following sentence to clarify the low rate of HCV genotyping:

Before: No text.

After (line 247-251): “Regarding molecular testing, out of 101 HTLV/HCV-coinfected individuals included, only 40 records contained information regarding molecular investigation (RNA-HCV), and 31 of these were submitted to HCV genotyping. The Brazilian Ministry of Health protocol recommends genotyping for patients who are initiating treatment, as well as those undergoing treatment who present resistance to antivirals [44].”

 

Reviewer #2: PONE-D-19-25685

Question 1 - Reviewer 2. Throughout the manuscript the authors present different estimates of prevalence of co-infection: (a) in the general population; (b) prevalence of HTLV given HCV infection (i.e. the denominator is HCV infected) and (c) prevalence of HCV given HTLV infection. These all have different denominators, interpretations and epidemiological significance. They cannot be compared, yet the authors do this. For example, the paragraph that starts on line 66 this - what are the authors comparing and what is it they are focused on? is it overall HCV/HTLV in the whole population? or one given the other, and if so which? This needs to be reconciled throughout the manuscript for studies cited and for the results. Then the conclusions can be better articulated and interpreted. Note that the Discussion also conflated these different approaches and the interpretation is flawed as a result. (eg, the paragraph starting on line 177: we don't know what the denominator is for the Sao Paulo study and then this is compared to Japan where author present the prevalence of HCV given HTLV infection).

Reply: Epidemiological studies on the rate of HTLV/HCV coinfection are extremely rare in Brazil. We initially observed that both HCV and HTLV are widespread in the state of Bahia, particularly in the city of Salvador in which two population-based studies were conducted to estimate the prevalence of these viruses. Only three studies that estimated the prevalence of HTLV/HCV coinfection were recovered in the scientific literature: one in the city of São Paulo and one in the city of Rio de Janeiro, both studies evaluated the coinfection of HTLV / HCV in individuals undergoing HCV treatment (Caterino De-Araujo et al., 2018); (Maciel and Mello, 2015). The third study was performed in the city of Ribeirão Preto / SP and evaluated for 11 years the seroprevalence of HTLV and co-infections with other STDs such as HIV, syphilis and HBV (Pinto et al., 2012). In the first two studies, the denominator was the number of HCV cases, in the last one the denominator was the number of HTLV cases. Our study is similar to studies conducted in Japan, in which the prevalence of HTLV / HCV coinfection was estimated in HTLV endemic areas (Nakashima et al., 1994; Boschi-Pinto et al., 2000) and in donor donors blood from Ribeirão Preto / SP (Pinto et al., 2012). We have modified the manuscript to make it clearly.

Results section:

Before: HCV infection was detected in 14.2% (101/713; 95% CI: 11.9-17.1) of the HTLV-positive individuals, versus 0.72% (855/119,331; 95% CI: 0.67 - 0.77) of the HTLV-negative samples (Figure 1).

After (line 144-146): HCV infection was detected in 14.2% (101/713; 95% CI: 11.9-17.1) of the HTLV-positive individuals, versus 0.72% (855/119,331; 95% CI: 0.67 - 0.77) of the HTLV-negative samples, p< 0.0001 (OR: 22.9; CI: 18.3 – 28.5) (Figure 1).

Discussion section:

Before: “The frequency of HTLV/HCV coinfection in the present study was slightly higher than that reported in São Paulo (5.3%), which is where more than one-half of all HCV-infected cases are concentrated in Brazil (20,34). However, this frequency was lower than rates found in two areas endemic for HTLV infection in Japan, in which around 25% of HTLV-1-infected individuals were also HCV-positive (12, 15).”

After (line 198-215): “The present study sought to determine the prevalence of HCV infection in a sample of HTLV-infected individuals. In Brazil, epidemiological data on the rate of HTLV/HCV coinfection remains scarce. Only three studies that estimated the prevalence of HTLV/HCV coinfection were recovered in the scientific literature: one in the city of São Paulo and one in the city of Rio de Janeiro, both studies evaluated the coinfection of HTLV / HCV in individuals undergoing HCV treatment [20,21]. The third study was performed in the city of Ribeirão Preto (São Paulo) and evaluated for 11 years the seroprevalence of HTLV and co-infections with other sexually transmitted diseases such as HIV, syphilis and HBV [22]. In the first two studies, the denominator was the number of HCV cases, in the last one the denominator was the number of HTLV cases. Our study is similar to studies conducted in Japan, in which the prevalence of HTLV / HCV coinfection was estimated in HTLV endemic areas [12,15] and in donor donors blood from Ribeirão Preto [22]. In contrast to our analysis, previous studies have evaluated HTLV infection in individuals with hepatitis C who received treatment [20,21]. We found that HTLV-positive individuals presented a significantly higher prevalence for anti-HCV and also had a higher probability of acquiring hepatitis C (OR: 22.9) compared to HTLV-negative individuals. Similar results were obtained on Iki Island in Japan, an endemic region for both viruses [12]. However, this difference was not observed in a study conducted in two southern Japanese villages, where HTLV and HCV are endemic [15].”

We have modified the conclusion as following:

Before: “In conclusion, the present study found that at least 14% of the individuals infected with HTLV in Bahia also harbor HCV. Coinfection was concentrated in males who resided in the microregions of Salvador, Ilhéus-Itabuna and Porto Seguro, all hotspots for HTLV infection. Given the clinical importance of identifying HTLV/HCV coinfection, new studies are needed to characterize the clinical and epidemiological profile of these individuals, in order to contribute to the prevention of these infections.”

After (line 272-277): “In conclusion, the present study found that at least 14% of the individuals infected with HTLV in Bahia also harbor HCV. Coinfection was concentrated in males who resided in the microregions of Salvador, Ilhéus-Itabuna and Porto Seguro, all hotspots for HTLV infection, although HTLV and HCV are widespread in the state. It is our hope that these findings will provide support for the implementation of measures to prevent infections caused by these viruses, especially in areas where higher rates of HTLV/HCV were described.”

 

Question 2 - Reviewer 2. The authors have not presented the main rationale for the study - why is this analysis important to public health and or clinical practice? What gap does this analysis fill and how should it be used to improve health or change policy?

Reply: The reviewer is correct in pointing out these deficiencies. Accordingly, we have included information in the introduction that highlights the importance of establishing the prevalence of coinfection with respect to impacts on clinical outcomes, treatment strategies and the epidemiology of co-infection between HTLV and HCV agents. Moreover, considering that the literature lacks substantial data regarding the prevalence of coinfection between HCV and HTLV, regardless of the denominator under consideration, our results provide support for the implementation of measures designed at preventing infections caused by these viruses in vulnerable populations, such as in individuals infected with HTLV, which is more prevalent in the state of Bahia than other regions in Brazil.

Before: “Brazil is endemic for both HTLV and HCV, and the presence of coinfection has been reported in several populations, especially those in Southeastern Brazil. The prevalence of HTLV in individuals infected with HCV ranges from 5.3% in São Paulo (20) to 7.5% in Rio de Janeiro (21). In addition, in blood donors, HCV was found in 35.9% of first-time HTLV-positive blood donors (22) and 1.5% in HTLV-positive men who have sex with men (23).

In light of considerations regarding the influence of HTLV/HCV coinfection on the outcome of either infection, the present study aimed to determine the rate of coinfection throughout the state of Bahia and map the geographical distribution of cases over a 10-year period.”

After (line 66-80): “…Brazil is endemic for both HTLV and HCV, and the presence of coinfection has been rarely reported in HCV patients undergoing treatment, as well as in blood donors, especially those in Southeastern Brazil. The prevalence of HTLV in individuals infected with HCV ranges from 5.3% in São Paulo [20] to 7.5% in Rio de Janeiro [21]. In addition, in blood donors, HCV was found in 35.9% of first-time HTLV-positive blood donors [22].

Contradictory clinical outcomes in the course of HTLV/HCV coinfection have been reported in Brazil and Japan. A better prognosis was described in coinfected Brazilian individuals who presented higher levels of Th1-type cytokines and CD4+ T lymphocytes, as well as lower hepatic fibrosis and alanine aminotransferase (ALT) [23–26]. Conversely, a Japanese study involving coinfected individuals described higher viral loads, a more rapid progression to hepatocellular carcinoma and a decreased response to treatment with interferon [15,27–30]. In light of considerations regarding the influence of HTLV/HCV coinfection on the outcome of either infection and a lack of epidemiologic studies, notably in the Brazilian Northeast macroregion, the present study aimed to determine the rate of coinfection throughout the state of Bahia and map the geographical distribution of cases over a 10-year period.”

New references have been added to support the statements above:

(line 372-375): 24. Abad-Fernández M, Moreno A, Dronda F, del Campo S, Quereda C, Casado JL, et al. Delayed liver fibrosis in HTLV-2-infected patients co-infected with HIV-1 and hepatitis C virus with suppressive antiretroviral therapy. AIDS. 2015; 29: 401-409. https://doi:10.1097/QAD.0000000000000555. PMID: 25565497.

(line 385-388): 27. Kamihira S, Momita S, Ikeda S, Yamada Y, Sohda H, Atogami S, et al. Cohort study of hepatotropic virus and human T lymphotropic virus type-I infections in an area endemic for adult T cell leukemia. Jpn J Med. 1991; 30: 492-497. https://doi:10.2169/internalmedicine1962.30.492. PMID: 1665877.

(line 389-392): 28. Kishihara Y, Furusyo N, Kashiwagi K, Mitsutake A, Kashiwagi S, Hayashi J. Human T lymphotropic virus type 1 infection influences hepatitis C virus clearance. J Infect Dis. 2001; 184: 1114-1119. Epub 2001 Sep 21. https://doi:10.1086/323890. PMID: 11598833.

(line 397-400): 30. Tokunaga M, Uto H, Oda K, Tokunaga M, Mawatari S, Kumagai K, et al. Influence of human T-lymphotropic virus type 1 coinfection on the development of hepatocellular carcinoma in patients with hepatitis C virus infection. J Gastroenterol. 2014; 49: 1567-1577. Epub 2014 Jan 25. https://doi:10.1007/s00535-013-0928-5 PMID: 24463696.

Question 3 - Reviewer 2 It would be very very good to know how the sample of people who were tested for BOTH viruses (which is the sample correct?) compare to the general population? it is hard to interpret this from what is presented. The authors state that because it is a large sample and it is noted that females are over-represented. I am assuming this is due to prenatal testing, but the authors should explain why this is. Several areas are 100% female samples. Then this needs to be better addressed in the limitations. The manuscript needs a table with demographics and primary outcome (HCV+HTLV exposure).

Reply: The authors are sympathetic to the reviewer’s request, and would sincerely like to offer robust prevalence rates for these infections in the general population for comparison purposes. However, since the LACEN laboratory, which is responsible for conducting these types of diagnoses throughout the state, is truly the only resource available capable of providing prevalence estimates, we regret that truly unbiased data with respect to the general population is not currently available. However, 120,192 individuals were included in the 10-year period of study, all of whom were tested for both HTLV and HCV viruses. The samples analyzed came from individuals who presented symptoms of infectious diseases, pregnant women or referred by blood banks, prisons and other health units of the public health system. In the state of Bahia, laboratory diagnosis of both HTLV and HCV are part of prenatal examinations, which certainly played a role in the greater representation of women in the study population. Although our sample is not representative of the general population due to these characteristics, it is in some way representative of the state as a whole with regard to the diversity of the data considered, since samples from 85.8% (358/417) municipalities of the state of Bahia were evaluated (total estimated state population: 15,126,371 inhabitants). Table 1 now includes the number of tested individuals per e municipality and the proposition of male/female.

Table 1 (lines 172-175)

Municipality Population* # performed tests

(%Female) Microregion # cases Age %Female Rate**

Terra Nova 12,467 224 (98) Catu 1 46 0 8.02

Itagi 14,084 151 (87) Jequié 1 48 100 7.10

Biritinga 14,129 580 (97) Serrinha 1 32 100 7.08

Ipiaú 43,169 1,496 (91) Ilhéus/Itabuna 2 57 0 4.63

Itabela 26,228 323 (93) Porto Seguro 1 47 0 3.81

Camacan 30,677 647 (70) Ilhéus/Itabuna 1 66 0 3.26

Esplanada 31,852 517 (98) Entre Rios 1 47 100 3.14

Morro do Chapéu 34,276 1,464 (92) Jacobina 1 27 100 2.92

Vera Cruz 35,951 231 (94) Salvador 1 56 100 2.78

Senhor do Bonfim 73,955 1,016 (74) Senhor do Bonfim 2 30 50 2.70

Salvador 2,920,679 30,001 (81) Salvador 78 54£ 44.8 2.67

São Sebastião do Passé 40,972 140 (86) Catu 1 39 100 2.44

Ipirá 60,891 2,831 (93) Feira de Santana 1 50 0 1.64

Brumado 63,391 276 (93) Brumado 1 40 100 1.58

Guanambi 77,691 595 (89) Guanambi 1 51 0 1.29

Santo Antônio de Jesus 86,014 1,644 (68) Santo Antônio de Jesus 1 51 100 1.16

Ilhéus 219,927 201 (56) Ilhéus/Itabuna 2 NA 50 0.91

Porto Seguro 117,402 306 (86) Porto Seguro 1 60 100 0.85

Teixeira de Freitas 121,268 1,181 (85) Porto Seguro 1 63 100 0.82

Lauro de Freitas 147,661 2,619 (87) Salvador 1 52 100 0.68

Juazeiro 234,082 93 (71) Juazeiro 1 33 100 0.43

TOTAL 101 2.8

Question 4 - Reviewer 2 A major limitation is that the authors are presenting prevalence of EXPOSURE to HCV - as they only present anti-HCV results. Unlike HTLV, HCV infection can be spontaneously cleared and treated. Thus this estimate does not reflect prevalence of infection, but prevalence of exposure. If authors had HCV RNA results this would be better to use for the prevalence of co-infection estimate.

Reply: Based on the cited reference below we respectfully request that the reviewer reconsider his/her criticism. Indeed, anti-HCV is the most common marker of hepatitis C infection, used to estimate its prevalence globally. In Brazil, it is one of the markers used to report cases of HCV infection in the SINAN (Brazil, 2019). Other studies previously conducted to estimate the prevalence of hepatitis C infection in Brazil and worldwide have also used anti-HCV for this purpose (Pereira et al., 2013; Catalan-Soares et al., 2014; Petruzziello et al., 2016). In the present study, we had information on RNAHCV data for 40 HTLV/HCV-coinfected individuals. Of these, 32 had detectable viral load.

Ministério da Saúde do Brasil. Boletim Epidemiológico - Hepatites virais. Brasília: Ministério da Saúde; 2018. Available: http://www.aids.gov.br.

Pereira LM, Martelli CM, Moreira RC, Merchan-Hamman E, Stein AT, Cardoso MR, et al. Prevalence and risk factors of Hepatitis C virus infection in Brazil, 2005 through 2009: a cross-sectional study. BMC Infect Dis. 2013; 13: 60. https://doi.org/10.1186/1471-2334-13-60 PMID: 23374914.

Petruzziello A, Marigliano S, Loquercio G, Cacciapuoti C. Hepatitis C virus (HCV) genotypes distribution: an epidemiological up-date in Europe. Infect Agent Cancer. 2016; 11: 53. https://doi:10.1186/s13027-016-0099-0 PMID: 27752280.

Before: No text.

After (line 263-271): “Another limitation is using anti-HCV serology instead HCV-RNA measurement to determine the prevalence of infection. Different of HTLV, infection by HCV may be spontaneously cleared and treated. However, anti-HCV is the most common marker of hepatitis C infection, used to estimate its prevalence globally. In Brazil, it is one of the markers used to report cases of HCV infection in the SINAN [44]. Other studies previously conducted to estimate the prevalence of hepatitis C infection in Brazil and worldwide have also used anti-HCV for this purpose [8,10,46]. In the present study, we had information on RNA-HCV data for 40 HTLV/HCV-coinfected individuals. Of these, 32 had detectable viral load.”

Question 5 - Reviewer 2 The low number of genotyped samples presents large interpretation issues: one because obviously only RNA positive samples can be genotyped, and there are potential biases resulting from (i) differential clearance rates of HCV found in HTLV-HCV infected persons, and (ii) potential differential clearance by genotype. This needs to be addressed in limitations.

Reply: The study is a retrospective evaluation of a 10-year period 2004-2013. The database originates from a laboratory surveillance service, where available data were evaluated. Regarding the molecular tests, we identified that of the 101 HTLV/HCV-coinfected individuals, there were records of molecular examinations (RNA-HCV) for 40 individuals, of which 31 had resulted from the HCV genotype. Genotyping according to the Ministry of Health protocol is recommended for patients on initiation of treatment or those in the course of treatment who are resistant to antivirals. We also believe that part of the lack of information is due to discontinuity of health care and death. However, a low number of HCV genotype samples were tested, possibly leading to a misinterpretation of results, since the HCV clearance rate may vary in HTLV infected persons and by genotype.

Material and Methods section:

Before: “No text.”

After (line 111-117): “With respect to molecular testing, RT-PCR (AMPLICOR MONITOR®, Roche Molecular Systems, Branchburg, NJ, USA) was employed in accordance with the manufacturer's specifications. Genotyping was performed by analyzing the highly conserved 5’ untranslated region using the Linear Array Hepatitis C Virus Genotyping Test (LiPA - Line Probe Assay - Roche Diagnostics, USA), following the manufacturer’s guidelines. This assay allows for the determination of six genotypes and subtypes (1a, 1b, 2, 2a, 2b, 3, 3a, 4, 4c, 5, 5a and 6).”

Discussion section:

Before: No text.

After (line 247-257): Regarding molecular testing, out of 101 HTLV/HCV-coinfected individuals included, only 40 records contained information regarding molecular investigation (RNA-HCV), and 31 of these were submitted to HCV genotyping. The Brazilian Ministry of Health protocol recommends genotyping for patients who are initiating treatment, as well as those undergoing treatment who present resistance to antivirals [44]. With respect to the profile of HCV circulating genotypes, the present study detected the presence of Genotypes 1 and 3, in 31 coinfected individuals. The most prevalent genotype was type 1 (83%). Accordingly, the HCV genotypes 1 and 3 are the most prevalent worldwide, accounting for about 46.2 and 30.1% of infections, respectively [45]. However, a low number of HCV genotype samples were tested, possibly leading to a misinterpretation of results, since the HCV clearance rate may vary in HTLV infected persons and by genotype.

Question 6 - Reviewer 2 Introduction: (a) line 62: specify that this is one study conducted in rural Ethiopia. If possible let reader know if urban Ethiopia has higher co-prevalence;

Reply: We thank the reviewer for his/her observation and have accordingly added the suggested information

Before: “However, this coinfection has not been reported rural areas (16). In Europe, where….”

After (line 61-62): “However, this coinfection has not been reported in Ethiopian rural areas (16). In Europe, where….

Question 7 - Reviewer 2 Introduction: (b) line 65 - the conclusion of the study in Spain regarding people who inject drugs; - did this study have any data on country of origin? in particular African origin?

Reply: The study population were composed of 351 individuals living in Barcelona, 422 in Madrid and 188 in Seville. Of these, 10.3% were foreigners, but do not report the country of origin.

Question 8 - Reviewer 2 If you don't have HCV RNA results, then the manuscript needs to specify that this is HCV exposure and not HCV infection.

Reply: Based on the cited reference below we respectfully request that the reviewer reconsider his/her criticism. Indeed, anti-HCV is the most common marker of hepatitis C infection, used to estimate its prevalence globally. In Brazil, it is one of the markers used to report cases of HCV infection in the SINAN (Brazil, 2019). Other studies previously conducted to estimate the prevalence of hepatitis C infection in Brazil and worldwide have also used anti-HCV for this purpose (Pereira et al., 2013; Catalan-Soares et al., 2014; Petruzziello et al., 2016). In the present study, we had information on RNAHCV data for 40 HTLV/HCV-coinfected individuals. Of these, 32 had detectable viral load.

Ministério da Saúde do Brasil. Boletim Epidemiológico - Hepatites virais. Brasília: Ministério da Saúde; 2018. Available: http://www.aids.gov.br.

Pereira LM, Martelli CM, Moreira RC, Merchan-Hamman E, Stein AT, Cardoso MR, et al. Prevalence and risk factors of Hepatitis C virus infection in Brazil, 2005 through 2009: a cross-sectional study. BMC Infect Dis. 2013; 13: 60. https://doi.org/10.1186/1471-2334-13-60 PMID: 23374914.

Petruzziello A, Marigliano S, Loquercio G, Cacciapuoti C. Hepatitis C virus (HCV) genotypes distribution: an epidemiological up-date in Europe. Infect Agent Cancer. 2016; 11: 53. https://doi:10.1186/s13027-016-0099-0 PMID: 27752280.

Question 9 - Reviewer 2 The Discussion needs to directly address how this data contributes to practice and or policy.

Reply: We concur entirely with the reviewer and we have included a statement in the Discussion section.

Before: “In conclusion, the present study found that at least 14% of the individuals infected with HTLV in Bahia also harbor HCV. Coinfection was concentrated in males who resided in the microregions of Salvador, Ilhéus-Itabuna and Porto Seguro, all hotspots for HTLV infection. Given the clinical importance of identifying HTLV/HCV coinfection, new studies are needed to characterize the clinical and epidemiological profile of these individuals, in order to contribute to the prevention of these infections.”

After (line 272-277): “In conclusion, the present study found that at least 14% of the individuals infected with HTLV in Bahia also harbor HCV. Coinfection was concentrated in males who resided in the microregions of Salvador, Ilhéus-Itabuna and Porto Seguro, all hotspots for HTLV infection, although HTLV and HCV are widespread in the state. It is our hope that these findings will provide support for the implementation of measures to prevent infections caused by these viruses, especially in areas where higher rates of HTLV/HCV were described.”

Attachment

Submitted filename: Response_to_Reviewers.docx

Click here for additional data file. (52.1KB, docx)

Decision Letter 1

William M Switzer

21 Apr 2020

PONE-D-19-25685R1

Distribution of Human T-Lymphotropic Virus (HTLV) and Hepatitis C Co-infection in Bahia, Brazil,

PLOS ONE

Dear PhD Santos,

Thank you for submitting your manuscript to PLOS ONE. After careful consideration, we feel that it has merit but does not fully meet PLOS ONE’s publication criteria as it currently stands. Therefore, we invite you to submit a revised version of the manuscript that addresses the points raised during the review process.

Specifically, please address the suggestions and comments of the reviewer raised in the current revision.

We would appreciate receiving your revised manuscript by Jun 05 2020 11:59PM. When you are ready to submit your revision, log on to https://www.editorialmanager.com/pone/ and select the 'Submissions Needing Revision' folder to locate your manuscript file.

If you would like to make changes to your financial disclosure, please include your updated statement in your cover letter.

To enhance the reproducibility of your results, we recommend that if applicable you deposit your laboratory protocols in protocols.io, where a protocol can be assigned its own identifier (DOI) such that it can be cited independently in the future. For instructions see: http://journals.plos.org/plosone/s/submission-guidelines#loc-laboratory-protocols

Please include the following items when submitting your revised manuscript:

  • A rebuttal letter that responds to each point raised by the academic editor and reviewer(s). This letter should be uploaded as separate file and labeled 'Response to Reviewers'.

  • A marked-up copy of your manuscript that highlights changes made to the original version. This file should be uploaded as separate file and labeled 'Revised Manuscript with Track Changes'.

  • An unmarked version of your revised paper without tracked changes. This file should be uploaded as separate file and labeled 'Manuscript'.

Please note while forming your response, if your article is accepted, you may have the opportunity to make the peer review history publicly available. The record will include editor decision letters (with reviews) and your responses to reviewer comments. If eligible, we will contact you to opt in or out.

We look forward to receiving your revised manuscript.

Kind regards,

William M. Switzer, MPH

Academic Editor

PLOS ONE

[Note: HTML markup is below. Please do not edit.]

Reviewers' comments:

Reviewer's Responses to Questions

Comments to the Author

1. If the authors have adequately addressed your comments raised in a previous round of review and you feel that this manuscript is now acceptable for publication, you may indicate that here to bypass the “Comments to the Author” section, enter your conflict of interest statement in the “Confidential to Editor” section, and submit your "Accept" recommendation.

Reviewer #1: All comments have been addressed

Reviewer #2: (No Response)

**********

2. Is the manuscript technically sound, and do the data support the conclusions?

The manuscript must describe a technically sound piece of scientific research with data that supports the conclusions. Experiments must have been conducted rigorously, with appropriate controls, replication, and sample sizes. The conclusions must be drawn appropriately based on the data presented.

Reviewer #1: Yes

Reviewer #2: Partly

**********

3. Has the statistical analysis been performed appropriately and rigorously?

Reviewer #1: Yes

Reviewer #2: Yes

**********

4. Have the authors made all data underlying the findings in their manuscript fully available?

The PLOS Data policy requires authors to make all data underlying the findings described in their manuscript fully available without restriction, with rare exception (please refer to the Data Availability Statement in the manuscript PDF file). The data should be provided as part of the manuscript or its supporting information, or deposited to a public repository. For example, in addition to summary statistics, the data points behind means, medians and variance measures should be available. If there are restrictions on publicly sharing data—e.g. participant privacy or use of data from a third party—those must be specified.

Reviewer #1: Yes

Reviewer #2: Yes

**********

5. Is the manuscript presented in an intelligible fashion and written in standard English?

PLOS ONE does not copyedit accepted manuscripts, so the language in submitted articles must be clear, correct, and unambiguous. Any typographical or grammatical errors should be corrected at revision, so please note any specific errors here.

Reviewer #1: Yes

Reviewer #2: Yes

**********

6. Review Comments to the Author

Please use the space provided to explain your answers to the questions above. You may also include additional comments for the author, including concerns about dual publication, research ethics, or publication ethics. (Please upload your review as an attachment if it exceeds 20,000 characters)

Reviewer #1: The authors have made a very diligent and thorough effort to address the comments and suggestions provided by the reviewers. As a result the quality of the manuscript has improved significantly.

Reviewer #2: The authors have mostly addressed my concerns and critiques in the revised submission, and I commend their attention to these. I have the following minor issues that I think need addressing to make the manuscript publishable.

1) The authors need to be explicit in the Methods section that this study used data from anti-HCV test results indicating exposure to HCV and that they are using this as a proxy for infection in their co-infection estimates. While they correctly noted in the limitations that clearance would result in fewer infections that estimated, this could be more explicitly stated in methods. Contrary to what they note, anti-HCV is not used globally to indicate infection, it is used to indicate exposure and previous infection. Many current systematic reviews use or estimate infection based on RNA results, or impute it based on expected clearance rates. Also as more people are treated, we can expect anti-HCV to be an even larger over-estimate of infection.

2) Lines 127-128: age) . authors say that they 'adjusted' the estimates. Adjusted for what? if its not adjusted, for example for age, then just say the rate per 100,000 and remove the "adjusted" . Also this sentence implies that your primary outcome is HCV and HTLV- co-infection among all tests reviewed. Not only HCV in those with HTLV. Is this correct?

3) The final conclusion is still weak: how can this data inform prevention? just hoping it will is not enough - what are ways that this paper can be used beyond their descriptive contribution?

**********

7. PLOS authors have the option to publish the peer review history of their article (what does this mean?). If published, this will include your full peer review and any attached files.

If you choose “no”, your identity will remain anonymous but your review may still be made public.

Do you want your identity to be public for this peer review? For information about this choice, including consent withdrawal, please see our Privacy Policy.

Reviewer #1: No

Reviewer #2: No

[NOTE: If reviewer comments were submitted as an attachment file, they will be attached to this email and accessible via the submission site. Please log into your account, locate the manuscript record, and check for the action link "View Attachments". If this link does not appear, there are no attachment files to be viewed.]

While revising your submission, please upload your figure files to the Preflight Analysis and Conversion Engine (PACE) digital diagnostic tool, https://pacev2.apexcovantage.com/. PACE helps ensure that figures meet PLOS requirements. To use PACE, you must first register as a user. Registration is free. Then, login and navigate to the UPLOAD tab, where you will find detailed instructions on how to use the tool. If you encounter any issues or have any questions when using PACE, please email us at figures@plos.org. Please note that Supporting Information files do not need this step.

PLoS One. 2020 Jul 21;15(7):e0223087. doi: 10.1371/journal.pone.0223087.r004

Author response to Decision Letter 1

3 Jun 2020

Question 1 - Reviewer #2: The authors need to be explicit in the Methods section that this study used data from anti-HCV test results indicating exposure to HCV and that they are using this as a proxy for infection in their co-infection estimates. While they correctly noted in the limitations that clearance would result in fewer infections that estimated, this could be more explicitly stated in methods. Contrary to what they note, anti-HCV is not used globally to indicate infection, it is used to indicate exposure and previous infection. Many current systematic reviews use or estimate infection based on RNA results, or impute it based on expected clearance rates. Also as more people are treated, we can expect anti-HCV to be an even larger over-estimate of infection.

Reply: We have included the following sentence in the methods section:

Before: no information.

After (line 127-130): The prevalence of HTLV / HCV coinfection was determined by taking into account the presence of HTLV and HCV antibodies. The presence of anti-HTLV indicates infection, while the presence of anti-HCV might indicate exposure and / or infection.

Question 2 - Reviewer #2: Lines 127-128: age) . authors say that they 'adjusted' the estimates. Adjusted for what? if its not adjusted, for example for age, then just say the rate per 100,000 and remove the "adjusted".

Reply: We thank the reviewer by his/her observation. We have removed “adjusted”. The rate means the number of infected individual per 100.000 habitants.

Before: “The adjusted rate of coinfection was expressed as the number of individuals infected per 100,000 inhabitants.”

After (line 130-131): “The rate of coinfection was expressed as the number of individuals infected per 100,000 inhabitants.”

Question 3 - Reviewer #2: The final conclusion is still weak: how can this data inform prevention? Just hoping it will is not enough - what are ways that this paper can be used beyond their descriptive contribution?

Reply: We have modified the conclusion as follows:

Before: “In conclusion, the present study found that at least 14% of the individuals infected with HTLV in Bahia also harbor HCV. Coinfection was concentrated in males who resided in the microregions of Salvador, Ilhéus-Itabuna and Porto Seguro, all hotspots for HTLV infection, although HTLV and HCV are widespread in the state. It is our hope that these findings will provide support for the implementation of measures to prevent infections caused by these viruses, especially in areas where higher rates of HTLV/HCV were described.”

After (line 276-287): “In conclusion, the present study evaluated a large number of individuals in Bahia, considered one of the states in Brazil most affected by HTLV infection. We found that at least 14% of the individuals infected with HTLV also harbor HCV. Coinfection was concentrated in males who resided in the microregions of Salvador, Ilhéus-Itabuna and Porto Seguro, all considered hotspots for HTLV infection, despite HTLV and HCV being widespread throughout the state. It is our hope that these findings will provide support for the implementation of preventive measures against the spread of these viruses, especially in areas where higher rates of HTLV/HCV coinfection were described. Moreover, as the presence of HTLV can negatively impact the course of HCV infection, the surveillance of active cases should be a priority in order to provide early treatment. The identification, control and prevention of the main risk factors associated with HTLV/HCV coinfection can lead to efficacious actions in a variety of epidemiological contexts specific to each affected region.”

Attachment

Submitted filename: Response_to_reviewers.docx

Click here for additional data file. (17.7KB, docx)

Decision Letter 2

William M Switzer

4 Jun 2020

PONE-D-19-25685R2

Distribution of Human T-Lymphotropic Virus (HTLV) and Hepatitis C Co-infection in Bahia, Brazil,

PLOS ONE

Dear Dr. Santos,

Thank you for submitting your manuscript to PLOS ONE. After careful consideration, we feel that it has merit but still does not fully meet PLOS ONE’s publication criteria as it currently stands. Therefore, we invite you to submit a revised version of the manuscript that addresses the minor points raised by one reviewer during the review process.

Please revise the manuscript in accordance with the additional minor recommendations of Dr. Page.

Please submit your revised manuscript by Jul 19 2020 11:59PM. If you will need more time than this to complete your revisions, please reply to this message or contact the journal office at plosone@plos.org. When you're ready to submit your revision, log on to https://www.editorialmanager.com/pone/ and select the 'Submissions Needing Revision' folder to locate your manuscript file.

Please include the following items when submitting your revised manuscript:

  • A rebuttal letter that responds to each point raised by the academic editor and reviewer(s). You should upload this letter as a separate file labeled 'Response to Reviewers'.

  • A marked-up copy of your manuscript that highlights changes made to the original version. You should upload this as a separate file labeled 'Revised Manuscript with Track Changes'.

  • An unmarked version of your revised paper without tracked changes. You should upload this as a separate file labeled 'Manuscript'.

If you would like to make changes to your financial disclosure, please include your updated statement in your cover letter. Guidelines for resubmitting your figure files are available below the reviewer comments at the end of this letter.

If applicable, we recommend that you deposit your laboratory protocols in protocols.io to enhance the reproducibility of your results. Protocols.io assigns your protocol its own identifier (DOI) so that it can be cited independently in the future. For instructions see: http://journals.plos.org/plosone/s/submission-guidelines#loc-laboratory-protocols

We look forward to receiving your revised manuscript.

Kind regards,

William M. Switzer, MPH

Academic Editor

PLOS ONE

Additional Editor Comments (if provided):

Please revise the manuscript in accordance with the additional minor recommendations of Dr. Page.

[Note: HTML markup is below. Please do not edit.]

[NOTE: If reviewer comments were submitted as an attachment file, they will be attached to this email and accessible via the submission site. Please log into your account, locate the manuscript record, and check for the action link "View Attachments". If this link does not appear, there are no attachment files.]

While revising your submission, please upload your figure files to the Preflight Analysis and Conversion Engine (PACE) digital diagnostic tool, https://pacev2.apexcovantage.com/. PACE helps ensure that figures meet PLOS requirements. To use PACE, you must first register as a user. Registration is free. Then, login and navigate to the UPLOAD tab, where you will find detailed instructions on how to use the tool. If you encounter any issues or have any questions when using PACE, please email PLOS at figures@plos.org. Please note that Supporting Information files do not need this step.

PLoS One. 2020 Jul 21;15(7):e0223087. doi: 10.1371/journal.pone.0223087.r006

Author response to Decision Letter 2

15 Jun 2020

Dear Editor,

Thank you very much for analyzing our manuscript. The replies to Editor’s comments are below:

Reviewer #2: The authors have mostly addressed my concerns and critiques in the revised submission, and I commend their attention to these. I have the following minor issues that I think need addressing to make the manuscript publishable.

Question 1 - Reviewer #2: The authors need to be explicit in the Methods section that this study used data from anti-HCV test results indicating exposure to HCV and that they are using this as a proxy for infection in their co-infection estimates. While they correctly noted in the limitations that clearance would result in fewer infections that estimated, this could be more explicitly stated in methods. Contrary to what they note, anti-HCV is not used globally to indicate infection, it is used to indicate exposure and previous infection. Many current systematic reviews use or estimate infection based on RNA results, or impute it based on expected clearance rates. Also as more people are treated, we can expect anti-HCV to be an even larger over-estimate of infection.

Reply: We have included the following sentence in the methods section:

Before: no information.

After (line 127-130): The prevalence of HTLV / HCV coinfection was determined by taking into account the presence of HTLV and HCV antibodies. The presence of anti-HTLV indicates infection, while the presence of anti-HCV might indicate exposure and / or infection.

Question 2 - Reviewer #2: Lines 127-128: age) . authors say that they 'adjusted' the estimates. Adjusted for what? if its not adjusted, for example for age, then just say the rate per 100,000 and remove the "adjusted". Also this sentence implies that your primary outcome is HCV and HTLV- co-infection among all tests reviewed. Not only HCV in those with HTLV. Is this correct?

Reply: We thank the reviewer by his/her observation. We have removed “adjusted”. The rate means the number of infected individual per 100.000 habitants. The rate means the number of infected individual per 100.000 habitants and our primary outcome is HCV and HTLV coinfection.

Before: “The adjusted rate of coinfection was expressed as the number of individuals infected per 100,000 inhabitants.”

After (line 130-131): “The rate of coinfection was the primary outcome and was expressed as the number of individuals infected per 100,000 inhabitants.”

Question 3 - Reviewer #2: The final conclusion is still weak: how can this data inform prevention? Just hoping it will is not enough - what are ways that this paper can be used beyond their descriptive contribution?

Reply: We have modified the conclusion as follows:

Before: “In conclusion, the present study found that at least 14% of the individuals infected with HTLV in Bahia also harbor HCV. Coinfection was concentrated in males who resided in the microregions of Salvador, Ilhéus-Itabuna and Porto Seguro, all hotspots for HTLV infection, although HTLV and HCV are widespread in the state. It is our hope that these findings will provide support for the implementation of measures to prevent infections caused by these viruses, especially in areas where higher rates of HTLV/HCV were described.”

After (line 277-288): “In conclusion, the present study evaluated a large number of individuals in Bahia, considered one of the states in Brazil most affected by HTLV infection. We found that at least 14% of the individuals infected with HTLV also harbor HCV. Coinfection was concentrated in males who resided in the microregions of Salvador, Ilhéus-Itabuna and Porto Seguro, all considered hotspots for HTLV infection, despite HTLV and HCV being widespread throughout the state. It is our hope that these findings will provide support for the implementation of preventive measures against the spread of these viruses, especially in areas where higher rates of HTLV/HCV coinfection were described. Moreover, as the presence of HTLV can negatively impact the course of HCV infection, the surveillance of active cases should be a priority in order to provide early treatment. The identification, control and prevention of the main risk factors associated with HTLV/HCV coinfection can lead to efficacious actions in a variety of epidemiological contexts specific to each affected region.”

Attachment

Submitted filename: Response_to_reviewers.docx

Click here for additional data file. (18.1KB, docx)

Decision Letter 3

William M Switzer

30 Jun 2020

Distribution of Human T-Lymphotropic Virus (HTLV) and Hepatitis C Co-infection in Bahia, Brazil,

PONE-D-19-25685R3

Dear Dr. Santos,

We’re pleased to inform you that your manuscript has been judged scientifically suitable for publication and will be formally accepted for publication once it meets all outstanding technical requirements.

Within one week, you’ll receive an e-mail detailing the required amendments. When these have been addressed, you’ll receive a formal acceptance letter and your manuscript will be scheduled for publication.

An invoice for payment will follow shortly after the formal acceptance. To ensure an efficient process, please log into Editorial Manager at http://www.editorialmanager.com/pone/, click the 'Update My Information' link at the top of the page, and double check that your user information is up-to-date. If you have any billing related questions, please contact our Author Billing department directly at authorbilling@plos.org.

If your institution or institutions have a press office, please notify them about your upcoming paper to help maximize its impact. If they’ll be preparing press materials, please inform our press team as soon as possible -- no later than 48 hours after receiving the formal acceptance. Your manuscript will remain under strict press embargo until 2 pm Eastern Time on the date of publication. For more information, please contact onepress@plos.org.

Kind regards,

William M. Switzer, MPH

Academic Editor

PLOS ONE

Additional Editor Comments (optional):

Reviewers' comments:

Acceptance letter

William M Switzer

8 Jul 2020

PONE-D-19-25685R3

Distribution of Human T-Lymphotropic Virus (HTLV) and Hepatitis C Co-infection in Bahia, Brazil,

Dear Dr. Santos:

I'm pleased to inform you that your manuscript has been deemed suitable for publication in PLOS ONE. Congratulations! Your manuscript is now with our production department.

If your institution or institutions have a press office, please let them know about your upcoming paper now to help maximize its impact. If they'll be preparing press materials, please inform our press team within the next 48 hours. Your manuscript will remain under strict press embargo until 2 pm Eastern Time on the date of publication. For more information please contact onepress@plos.org.

If we can help with anything else, please email us at plosone@plos.org.

Thank you for submitting your work to PLOS ONE and supporting open access.

Kind regards,

PLOS ONE Editorial Office Staff

on behalf of

Mr. William M. Switzer

Academic Editor

PLOS ONE

Associated Data

    This section collects any data citations, data availability statements, or supplementary materials included in this article.

    Supplementary Materials

    S1 Table. Anonymized data set comprised of HTLV and HCV tested individuals living in Bahia, Brazil from 2004 to 2013.

    (XLSX)

    Click here for additional data file. (11.1MB, xlsx)
    Attachment

    Submitted filename: Response_to_Reviewers.docx

    Click here for additional data file. (52.1KB, docx)
    Attachment

    Submitted filename: Response_to_reviewers.docx

    Click here for additional data file. (17.7KB, docx)
    Attachment

    Submitted filename: Response_to_reviewers.docx

    Click here for additional data file. (18.1KB, docx)

    Data Availability Statement

    All relevant data are within the manuscript and its Supporting Information files.

    Articles from PLoS ONE are provided here courtesy of PLOS

    RESOURCES