Abstract
Dengue is a global epidemic causing over 100 million cases annually. The clinical symptoms range from mild fever to severe hemorrhage and shock, including some fatalities. The current paradigm is that these severe dengue cases occur mostly during secondary infections due to antibody-dependent enhancement after infection with a different dengue virus serotype. India has the highest dengue burden worldwide, but little is known about disease severity and its association with primary and secondary dengue infections. To address this issue, we examined 619 children with febrile dengue-confirmed infection from three hospitals in different regions of India. We classified primary and secondary infections based on IgM:IgG ratios using a dengue-specific enzyme-linked immunosorbent assay according to the World Health Organization guidelines. We found that primary dengue infections accounted for more than half of total clinical cases (344 of 619), severe dengue cases (112 of 202) and fatalities (5 of 7). Consistent with the classification based on binding antibody data, dengue neutralizing antibody titers were also significantly lower in primary infections compared to secondary infections (P ≤ 0.0001). Our findings question the currently widely held belief that severe dengue is associated predominantly with secondary infections and emphasizes the importance of developing vaccines or treatments to protect dengue-naive populations.
Dengue infections have greatly increased in India during the past two decades and India now has the largest number of dengue cases globally1. However, not much is known about the proportion of primary versus secondary dengue infections and how this correlates with disease severity. In this study, we examined children with confirmed febrile dengue from three hospitals in different regions of India. Three tertiary care centers in India—St. John’s Research Institute (SJRI), All India Institute of Medical Sciences (AIIMS) and Christian Medical College (CMC)—participated in this study, where 619 children with confirmed dengue were studied between 2012 and 2018. The characteristics of these patients are shown in Extended Data Table 1. Recruitment was done from 2014 to 2016 (SJRI), 2012 to 2018 (AIIMS) and 2015 to 2017 (CMC). The age of the children ranged from 2 months to 16 years; all the sites included both males and females. The infecting dengue virus serotype was identified in about 65% of patients and infections were seen with Dengue virus 1 (DENV-1) (n = 188), DENV-2 (n = 143), DENV-3 (n = 55) and DENV-4 (n = 8). Patients with confirmed dengue were classified as either primary or secondary dengue infection based on the ratio of the index value of dengue-specific plasma IgM and IgG using standard-capture enzyme-linked immunosorbent assays (ELISAs) (Panbio) as per the World Health Organization (WHO) guidelines2. Analysis of primary versus secondary infection status at all three clinical sites showed that patients consisted of a mix of primary (344 of 619) and secondary (275 of 619) infections (Extended Data Table 2). This mix of primary and secondary infections was seen at each of the individual sites.
We then determined disease severity in these patients using the WHO 2009 guidelines of dengue infection without warning signs, dengue infection with warning signs and severe dengue infection2. Of the 619 children with confirmed dengue who were examined, 202 (32.6%) had severe dengue, 363 (58.6%) exhibited dengue infection with warning signs and 54 (8.7%) had dengue infection without warning signs (Extended Data Table 3). Of importance was the finding that the frequency of severe disease cases was essentially similar in patients with primary (32.5%) versus secondary (32.7%) infections. These data show that disease severity was not preferentially associated with secondary infections in this study (Fig. 1a). This trend of severe dengue during primary infection was not unique to a single site but was seen at all three clinical site (Extended Data Table 4). Also, severe dengue during both primary and secondary infection was not associated with a particular DENV serotype and was seen with DENV-1, DENV-2 and DENV-3 infections (Extended Data Table 5). There were very few (n = 8) DENV-4 infections to make any conclusions about this serotype (Extended Data Table 1).
Fig. 1. Similar frequency of severe disease in pediatric patients with primary versus secondary dengue infections.
a, Frequency of severe dengue infection, dengue infection with warning signs or dengue infection without warning signs cases among children with confirmed dengue (all cases, n = 619) and among those classified as primary (n = 344) or secondary (n = 275) dengue infection as described in the Methods. Disease severity was not significantly different between primary and secondary cases (P = 0.53, Fisher’s exact test). Testing the frequency of severe dengue between primary and secondary cases also yielded nonsignificant result (P = 1.0, two-sided Fisher’s exact test). The 95% confidence intervals (CIs) for the percentages are: all cases, dengue infection without warning signs = 6.7–11.2, dengue infection with warning signs = 54.7–62.5, severe dengue infection = 29.1–36.4; primary, dengue infection without warning signs = 6.9–13.2, dengue with warning signs = 52.3–62.7, severe dengue infection = 28.1–38.0; secondary, dengue infection without warning signs = 5.0–11.4, dengue with warning signs = 54.1–65.6, severe dengue infection = 27.1–38.1 (Wilson score interval). b, Pie chart showing severe dengue infection, dengue infection with warning signs and dengue infection without warning signs case frequency among children with primary dengue infection who were recruited on or before day 4 after the onset of symptoms and were below detection for dengue-specific IgG using the Panbio Capture ELISA (n = 126). The 95% CIs for the percentages are: dengue infection without warning signs = 16.2–29.9, dengue infection with warning signs = 36.6–52.9, severe dengue infection = 25.8–41.3; (Wilson score interval). c, Disease severity and incidence of primary and secondary infections as a function of age. The bar graph shows the frequency of primary dengue infections according to age. The number of patients in each age group is indicated in the graph. Infants (1 year old or younger) were all primary infections, which is notably different from the approximately equal mix seen in the older groups (P ≤ 0.00001, two-sided Fisher’s exact test). d, Bar graph showing the frequency of severe disease cases in the different age groups. Patients aged 1 year or younger were more likely to have severe dengue compared to older patients (P ≤ 0.002, two-sided Fisher’s exact test). e, Pie charts showing the frequency of primary versus secondary infections among severe disease cases in the indicated age groups.
During these studies, seven fatalities were reported at the AIIMS site (Extended Data Table 6). These patients were all characterized as having severe disease at the time of admission; fatalities occurred within 24–48 h after admission. Five of the seven fatalities were associated with primary dengue infections and two with secondary infections. The IgM:IgG ratios for these patients are shown in Extended Data Table 6.
Our results showing similar frequencies of severe disease in primary and secondary dengue infections was an interesting but surprising finding. To address this issue more rigorously, we increased the classification stringency by using a higher value of IgM:IgG dengue anti-body ratio from the WHO-recommended value of 1.2 or higher (as used in Fig. 1a) to 1.32 or 1.4 and 1.78 (Extended Data Fig. 1)2. Interestingly, even after increasing the ratio of dengue-specific IgM:IgG antibody to 1.78, the percentage of severe dengue cases in primary infections was comparable (32.5% at the 1.2 ratio versus 33.6% at the 1.78 ratio). Also, the percentage of severe disease cases at the 1.78 cutoff in primary versus secondary infections was highly similar with 33.6% in primary versus 31.9% in secondary infections. As an even more stringent criteria for defining a primary infection, we looked at dengue cases analyzed at early time points after the onset of symptoms (on or before day 4) and were IgG− at that time for dengue antibody using capture ELISA but IgM+ for dengue antibody. These IgG− IgM+ patients also showed similar frequency (35.7%) of severe disease (Fig. 1b), thus providing compelling evidence of severe disease during primary dengue infection. Also, we further verified that primary infections accounted for a substantial proportion of severe dengue cases by using both the older WHO 1997 disease classification and the newer WHO 2009 classification criteria2–4 (Extended Data Fig. 2).
We next examined the relative proportions of primary versus secondary dengue infections and disease severity as a function of age. All dengue patients aged 1 year or younger were primary infections whereas the older age groups (years 1–3, 4–6, 7–9, 10–12 and 13 or older) were an equal mix of primary and secondary infections (Fig. 1c). Disease severity was the highest in children aged 1 year or younger compared to older children, where roughly 30% had severe disease (Fig. 1d). It is possible that primary dengue infection might cause severe disease in infants whereas in older children severe disease might predominantly be due to secondary dengue infection. However, this was not the case. Stratification of the data according to age showed that 46.7% of severe disease cases were primary dengue infections in children aged between 1 and 3 years; 50.3% of severe dengue cases were primary dengue infections among children aged 4–16 years (Fig. 1e). Thus, severe dengue was seen during primary dengue infections irrespective of age in these pediatric patients.
It has been proposed that severe dengue in infants is due to the presence of maternal IgG antibodies that cause antibody-dependent enhancement (ADE)5. Because more than 60% (22 of 34) of children younger than 1 year had severe disease, we looked at their dengue-specific antibody responses in more detail (Extended Data Fig. 3). Based on the Panbio ELISA, none of these young children (n = 34) had any detectable IgG antibody but all were positive for dengue-specific IgM (Extended Data Fig. 3a). Also, neutralizing antibody responses were either low or mostly undetectable in these infants (Extended Data Fig. 3b). We next asked whether IgM levels or neutralizing activity differed in infants with severe dengue infection compared to nonsevere cases. Neither IgM levels (Extended Data Fig. 3c) nor neutralizing antibody responses (Extended Data Fig. 3d) differed significantly depending on disease severity in these infants with primary dengue infection.
To understand if any differences exist in the levels of dengue neutralizing antibody responses during the acute febrile period in children with primary versus secondary dengue infections, we measured the neutralizing antibody titers against each dengue virus serotype (DENV-1, DENV-2, DENV-3 and DENV-4). Samples from children who were categorized as primary infections using capture ELISA showed significantly lower (P ≤ 0.0001) neutralizing antibody titers for each dengue serotype compared to the samples from children with secondary dengue infection (Fig. 2a). Additionally, samples from children with primary infection (Fig. 2b, left) showed a much narrower breadth of the neutralizing antibody response compared to samples from children with secondary infection (Fig. 2b, right). Analysis of children whose infecting serotype was identified showed that the neutralizing titers to the infecting serotype and for the noninfecting serotypes were below detection or significantly lower in children who were categorized as having primary infections compared to those classified as having secondary infections (Fig. 2c and Extended Data Fig. 4).
Fig. 2. Comparison of neutralizing antibody responses between cases with primary and secondary dengue infection.
a, Neutralizing antibody titers against each of the four dengue virus serotypes (DENV-1, DENV-2, DENV-3 and DENV-4) in the plasma of a subset of patients from the AIIMS site with primary (n = 41) or secondary (n = 67) dengue infection. P values were calculated using a two-sided Mann–Whitney U-test. b, Breadth of neutralizing antibody response in individual cases with primary (left) and secondary (right) dengue infection from a. Individual patients were stratified from the highest neutralizing titer to any of the four serotypes. The infecting serotype, where known, is indicated by closed symbols. c, Neutralizing antibody titers against the infecting virus serotype and heterologous serotypes in primary (n = 35) and secondary (n = 41) dengue infection from a subset of patients in a, where the infecting serotype was DENV-2. P values were calculated using a two-sided Mann–Whitney U-test.
It is worth considering our findings in the context of other related studies. Historical studies from Southeast Asia and Cuba attributed the vast majority of dengue hemorrhagic fever/dengue shock syndrome cases to secondary dengue infections6–8. However, other studies concluded that primary infections can also cause severe disease and fatalities9,10. This interesting and important issue has been much debated; however, during the past several years, many in vitro and animal model studies provided evidence for ADE as a potential mechanism for severe dengue11,12. In addition, a more recent study using a cohort in Nicaragua showed enhanced disease in individuals who had an intermediate level of preexisting dengue virus-specific antibody13. Thus, the prevailing consensus in the field is that severe dengue is tightly linked to secondary dengue infections. Our study of pediatric dengue infections in India shows that severe disease is also seen in primary infections. The results of our study do not necessarily question ADE or the presentation of severe disease during secondary dengue; rather, they highlight that primary infections can also be a major contributor to the dengue disease burden.
It is important to discuss some of the limitations of our study. The Panbio capture ELISA assay we used in this study is standardized and widely used all over the world for classifying primary versus secondary dengue infections; however, it is not the most sensitive assay14–16. Thus, we cannot rule out potential misclassification in some of the primary cases. Also, we cannot make any definitive statements about maternal antibodies using this Panbio assay. Finally, our study was conducted in tertiary clinical centers and may not necessarily predict what is happening at the population level in the community17. Future studies using well-designed cohort-based studies are needed to address this important question. We hope that the interesting results from our study of more than 600 patients from tertiary care hospitals in three different geographical areas of India will provide the impetus for carrying out larger community-level, population-based studies in India.
Our studies are relevant to the ongoing global dengue vaccine development efforts that are strongly influenced by the view that severe dengue is overwhelmingly seen during secondary infection18–20. Hence, dengue vaccine trials are often done in seropositive individuals to boost their immunity; recently approved dengue vaccines are mostly licensed for seropositive individuals18. Our results show that primary dengue infections can also constitute a substantial fraction of the burden of severe disease. Thus, there is an urgent need for an effective dengue vaccine that can be safely used in dengue-naive individuals.
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Any methods, additional references, Nature Portfolio reporting summaries, source data, extended data, supplementary information, acknowledgements, peer review information; details of author contributions and competing interests; and statements of data and code availability are available at https://doi.org/10.1038/s41591-024-02798-x.
Methods
Study oversight and sample acquisition
Our research complies with all relevant ethical regulations and was approved by Institutional Ethics Committees of AIIMS, SJRI and CMC, where the patients were recruited. A total of 619 cases with confirmed dengue infection in children younger than 17 years recruited from three different tertiary clinical sites located in diverse geographical regions of India are included in this analysis. This included the SJRI (n = 380, during 2014–2016) located in Southern India, the AIIMS (n = 200, during 2012–2018) located in Northern India, and CMC (n = 39, during 2015–2017) located in Southeastern India. Written informed consent was obtained from the parent or guardian of the child; verbal assent was obtained from children aged 8 years and older. Participation in the study was voluntary. Children eligible for enrollment at the SJRI site were those admitted to the inpatient pediatric unit with a clinical diagnosis of dengue, which was made by the treating physician using the WHO 2009 guidelines. Eligible children at the AIIMS and CMC sites were those admitted to the inpatient pediatric unit with a clinical diagnosis of dengue and those reporting to the outpatient center with mild dengue as determined by a combination of clinical diagnosis and a positive rapid test for dengue nonstructural protein 1 (NS1)/IgM or IgM ELISA. Cases positive for malaria were excluded. No previous medical records or information was available regarding a history of past confirmed or suspected dengue infections. Inclusion criteria consisted of being aged from 1 month to 17 years at the SJRI site, or 4–14 years at the AIIMS and CMC sites, a clinical diagnosis of dengue, written informed consent by the parent or guardian of the child, and verbal assent from children aged 8 years and older. Blood samples obtained to perform routine hospital screening were evaluated for stringent laboratory confirmation of recent dengue virus infection and negativity for chikungunya IgM and malaria antigens as outlined in the following sections. A total of 619 patients, consisting of 355 males and 264 females, with confirmed dengue virus infection and negative for chikungunya IgM and malaria antigen were included in this analysis. Individualized de-identified data on age, sex and clinical disease classification of the patients analyzed in this study are provided as supplementary source data. All raw data are provided as source files or presented in the main text or extended data.
Disease characterization
Based on extensive clinical laboratory tests and evaluation, the attending physicians at each clinical site classified the dengue disease grade based on the WHO 2009 guidelines as dengue infection without warning signs (DI), dengue infection with warning signs (DW) and severe dengue infection (SD)2 at the time of recruitment. The disease grade compiled by the attending physician was not disclosed to the researchers until the end of the study, allowing for a blinded study.
Plasma isolation
Blood samples were collected in Vacutainer CPT tubes (catalog no. 362761, BD Biosciences). Plasma was separated as described in previous studies21.
Dengue confirmation
Laboratory confirmation of dengue infection was based on positivity to one or more of the following: dengue NS1 capture ELISA (catalog no. IR31048, J Mitra), dengue IgM Capture ELISA (catalog no. 01PE20, Panbio) and dengue real-time PCR. Only patients who were positive for dengue NS1 or IgM or PCR, and negative for chikungunya IgM strip test (catalog no. IR061010, J Mitra) and negative for malaria antigen ELISA (catalog no. 05EK40, SD Bioline), were included in this analysis.
Characterization of primary and secondary infections
Primary and secondary infections were classified using standard Panbio Capture ELISAs (catalog nos. 01PE10 and 01PE20) that quantify IgM and IgG ratios in plasma diluted 1:100. In patients who were seronegative in the first sampling, a second febrile bleed was used to classify primary versus secondary status. Unless otherwise mentioned, and according to the WHO criteria, within confirmed dengue patients, primary dengue infections were those that did not induce detectable levels of antibodies in the subsequent two samples or had an IgM:IgG ratio of 1.2 or higher and secondary infections were those that had an IgM:IgG ratio of less than 1.2 (ref. 2).
Dengue virus neutralization using focus-forming assay
The neutralization capacity of plasma samples against each of the dengue virus serotypes (DENV-1, DENV-2, DENV-3 and DENV-4) was determined using a focus-forming assay as described previously22. Plasma was heat-inactivated at 56 °C for 30 min. Serially diluted plasma (1:100–1:102,400) was incubated with 100 focus-forming units of virus for 1 h at 37 °C. Vero cell monolayers were infected with the plasma–virus mixture for 1 h at 37 °C. An overlay containing 2% carboxymethyl-cellulose was added to the infected cells. After 72 h, cells were fixed and then stained with anti-flavivirus monoclonal antibody 4G2 (catalog no. MAB10216, Merck Millipore) followed by detection with horseradish peroxidase-linked anti-mouse IgG (catalog no. 7076S, Cell Signaling Technology). Foci were developed using TrueBlue Peroxidase (catalog no. 50-78-02, KPL) as a substrate. Neutralizing antibody titers were calculated as the reciprocal of the plasma dilution where 50% reduction in foci was observed. Samples in which at least a 50% reduction in foci was not seen at 1:50 dilution were considered below the assay cutoff and were assigned a value of 1:40.
Serotype determination
Viral RNA was extracted from 120 μl whole blood and the dengue virus serotype was detected based on previously published protocols23.
Statistical analysis
Data were analyzed using R v.4.3.1 and Prism 6 (GraphPad Software). P < 0.05 was considered statistically significant.
Ethics and inclusions
Clinical data pertaining to this study were collected in India. Thirty colleagues, including the senior authors (R.L., A.S. and AC.), are from India. We fully endorse and are committed to the guidance of the Nature Portfolio journals on low- and middle-income country authorship and inclusion.
Our research complies with all relevant ethical regulations and was approved by Institutional Ethics Committees of AIIMS, SJRI and CMC, where patients were recruited. Study participation was voluntary. The data collection and analysis techniques used raised no risks pertaining to incrimination, discrimination, the environment, health, safety, security or other personal risks. No cultural artifacts or associated traditional knowledge has been transferred out of any country. This research is locally relevant to India and globally.
Reporting summary
Further information on research design is available in the Nature Port-folio Reporting Summary linked to this article.
Extended Data
Extended Data Fig. 1. Similar frequency of severe disease in primary versus secondary cases that were distinguished using stringent IgM/IgG ratios.
Pie charts show the frequency of Severe Dengue (SD), Dengue with warning signs (DW) and Dengue infection without warning signs (DI) cases in primary versus secondary dengue infections that were distinguished using more stringent IgM/IgG ratios indicated on left. The number of patients in each group is indicated below the pie chart. For all three classification methods, the proportion of severe disease was not significantly different between primary and secondary cases (p > 0.78, two-sided Fisher’s exact test). The 95% confidence interval for the percentages indicated in the pie charts are as below: IgM/IgG >1.32, primary: DI- 5.4-11.6, DW-53.4-64.4, SD-27.9-38.5, Secondary: DI- 6.7-13.1, DW-52.8-63.6, SD-27.4-37.6; IgM/IgG >1.4: primary: DI- 5.7-12.1, DW-52.2-63.5, SD-28.5-39.3, secondary: DI- 6.4-12.6, DW-53.8-64.4, SD-26.9-36.9; IgM/IgG >1.78: primary: DI- 5.8-13.0, DW-50.5-62.9, SD-28.7-40.6 and secondary: DI- 6.3-12.0, DW-54.8-64.6, SD-27.0-36.3 (Wilson CI).
Extended Data Fig. 2. Frequency of severe disease in primary versus secondary dengue infections using WHO 1997 and WHO 2009 disease classification.
Data from a subset of the patients from the AIIMS Delhi site where disease severity was classified using both WHO 2009 and WHO 1997 criteria. a, Data shown by WHO 1997 disease classification. Pie charts show the frequency of the cases with dengue shock syndrome (DSS), dengue hemorrhagic fever (DHF); or dengue fever (DF) among a subset of dengue confirmed children that are recruited from AIIMS site among all cases (n = 171), primary dengue cases (n = 66) and secondary dengue cases (n = 105). DSS case frequency is not significantly different between the primary and secondary dengue infections, (p = 0.106, two-sided Fisher’s exact test). b, Data shown by WHO 2009 disease classification among the same group of the patients from panel a. Pie charts show the frequency of the cases with severe dengue (SD), dengue with warning signs (DW); or dengue infection without warning signs (DI) among all cases, primary dengue cases or secondary dengue cases. Severe dengue case frequency was not significantly different between the primary and secondary dengue infections, (p = 0.344, two-sided Fisher’s exact test).
Extended Data Fig. 3. Dengue specific responses in infants (≤1-year-old).
a, Scatter plot shows dengue specific IgM and IgG index values by capture Elisa (Panbio) for dengue confirmed infants (n = 34). p values were calculated using two-sided Mann-Whitney U tests b, Neutralizing antibody titers to the indicated infecting virus serotype in dengue confirmed infants where the infecting serotype was determined (n = 26). c. Scatter plots show dengue specific IgM index values by Panbio Capture ELISA among the infants with different grades of disease severity. Severe dengue (SD, n = 22); Dengue with warning signs (DW, n = 12). Note that there are no Dengue infection without warning signs (DI) cases since all the hospitalized infants were either SD or DW cases. p values (p = 0.087) were calculated using two-sided Mann-Whitney U tests. Non-significant p values (>0.05) are indicated as n.s. d. Scatter plots show neutralizing activity against the indicated infecting dengue virus serotypes among the infants with different grades of disease severity. Severe dengue (SD, n = 15); Dengue with warning signs (DW, n = 11). Note that there are no DI cases since all of the hospitalized infants were either SD or DW cases. p values (p > 0.999) were calculated using two- sided Mann-Whitney U tests. Non-significant p values (>0.05) are indicated as n.s.
Extended Data Fig. 4. Neutralization responses were below detection or significantly lower for infecting serotype in the primary dengue cases compared to secondary dengue cases.
Neutralizing antibody titers against the infecting virus serotype in primary (n = 38) and secondary (n = 50) from a subset of the patients from 2b, where the infecting serotype was identified. p values were calculated using Mann-Whitney U test.
Extended Data Table 1. Characteristics of dengue-infected patients.
| Characteristics of the dengue infected patients (n=619). | ||||
|---|---|---|---|---|
| Clinical Sites | ||||
| All Sites Pooled (n=619) |
SJRIa Bengaluru (n=380) |
AIIMSb Delhi (n=200) |
CMCc Vellore (n=39) |
|
| Male/Female (n) | 355/264 | 227/153 | 105/95 | 23/16 |
| Age in years, average (Range) | 7.9 (0.2-16.1) | 7.1 (0.2–16.1) | 9.3 (4-14) | 8.7 (4-14) |
| Day of symptoms, average (Range) | 4.4 (2-13) | 4.3 (2–7) | 4.4 (2–7) | 6.6 (3-13) |
| Serotype determined, n | 411 | 257 | 154 | |
| DENV-1, n (%) | 188 (45.7%) | 183 (71.2%) | 5 (3.2%) | |
| DENV-2, n (%) | 143 (34.7%) | 48 (18.6%) | 95 (61.7%) | |
| DENV-3, n (%) | 55 (13.4%) | 12 (4.6%) | 43 (27.9%) | |
| DENV-4, n (%) | 8 (1.9%) | 2 (0.8%) | 6 (3.9%) | |
| >1 serotype, n (%) | 17 (4.1%) | 12 (4.7%) | 5 (3.2%) | |
| Serotype not determined, n | 208 | 123 | 46 | 39 |
SJRI- St. John’s Research Institute.
AIIMS- All India Institute of Medical Sciences.
CMC- Christian Medical College.
Extended Data Table 2. Primary versus secondary infection status of patients with confirmed dengue infection.
| Primary versus secondary infection status of the dengue confirmed patients. | ||
|---|---|---|
| Clinical site* | Primary n(%) |
Secondary n(%) |
| All sites (n=619) | 344 (55.6%) | 275 (44.4%) |
| SJRI, Bengaluru (n=380) | 239 (62.9%) | 141 (37.1%) |
| AllMS, Delhi (n=200) | 86 (43%) | 114 (57%) |
| CMC, Vellore (n=39) | 19 (48.7%) | 20 (51.2%) |
SJRl- St. John’s Research Institute.
AIIMS- All India Institute of Medical Sciences.
CMC- Christian Medical College.
Extended Data Table 3. Disease characteristics of patients with confirmed dengue infection.
| Disease characteristics of the dengue confirmed patients (n=619). | ||||
|---|---|---|---|---|
| Clinical Site | ||||
| All Sites Pooled (n=619) |
SJRIa Bengaluru (n=380) |
AIIMSb Delhi (n=200) |
CMCc Vellore (n=39) |
|
| Severe Dengue (SD)* | 202 (32.6%) | 114 (30.0%) | 83 (41.5%) | 5 (12.8%) |
| Dengue Warning (DW)* | 363 (58.6%) | 262 (68.9%) | 73 (36.5%) | 28 (71.8%) |
| Dengue Infection (DI)* | 54 (8.7%) | 4(1.1%) | 44 (22.0%) | 6 (15.3%) |
based on WHO 2009 disease severity classification.
SJRI- St. John’s Research Institute.
AIIMS- All India Institute of Medical Sciences.
CMC- Christian Medical College.
Extended Data Table 4. Disease severity between primary and secondary dengue infection at individual clinical sites.
| Disease severity among primary versus secondary dengue infections at individual clinical sites. | ||||
|---|---|---|---|---|
| Clinical Site* | Primary/Secondary | Disease severity | ||
| Severe Dengue n(%) |
Dengue Warning n (%) |
Dengue Infection n(%) |
||
| SJRI, Bengaluru | Primary (n=239) | 77 (32.2%) | 160 (66.94%) | 2 (0.83%) |
| Secondary (n=141) | 37 (26.2%) | 102 (72.3%) | 2 (1.41%) | |
| AllMS, Delhi | Primary (n=86) | 31 (36.04%) | 27 (31.39%) | 28 (32.55%) |
| Secondary (n=114) | 52 (45.61%) | 46 (40.35%) | 16 (14.03%) | |
| CMC, Vellore | Primary (n=19) | 4 (21.05%) | 11 (57.89%) | 4 (21.05%) |
| Secondary (n=20) | 1 (5%) | 17 (85%) | 2 (10%) | |
SJRI- St. John’s Research Institute.
All MS- All India Institute of Medical Sciences.
CMC- Christian Medical College.
Extended Data Table 5. Disease severity between patients with primary and secondary dengue infection depending on dengue serotype.
| Disease severity among primary versus secondary dengue infected patients depending on the dengue serotype. | ||||
|---|---|---|---|---|
| Serotype* | Primary/Secondary | Disease severity, n(%) | ||
| Severe Dengue | Dengue Warning | Dengue Infection | ||
| DENV-l | Primary (n=143, 76.1%) | 47 (32.9%) | 93 (65.0%) | 3 (2.1%) |
| Secondary (n=45, 23.9%) | 14 (31.1%) | 31 (68.9%) | 0 (0%) | |
| DENV-2 | Primary (n=75, 52.4%) | 26 (34.7%) | 33 (44.0%) | 16 (21.3%) |
| Secondary (n=68, 47.6%) | 33 (48.5%) | 30 (44.1%) | 5 (7.4%) | |
| DENV-3 | Primary (n=26, 47.3%) | 12 (46.2%) | 9 (34.6%) | 5 (19.2%) |
| Secondary (n=29, 52.7%) | 12 (41.4%) | 14 (48.3%) | 3 (10.3%) | |
From PCR confirmed cases.
Extended Data Table 6. Fatalities in primary and secondary dengue infections.
| Fatalities in primary and secondary dengue infections. | |||||||
|---|---|---|---|---|---|---|---|
| Patient | Primary/Secondary | Age (years) | Infecting Serotype | Day of fatality post onset of symptoms* | Panbio Capture ELISA | ||
| IgM** | IgG*** | IgM/lgG$ | |||||
| Patient 1 | Primary | 9 | DENV-2 | 6 | 0.31 | 0.12 | - |
| Patient 2 | Primary | 9 | DENV-3 | 5 | 6.65 | 2.74 | 2.42 |
| Patient 3 | Primary | 8 | DENV-2 | 4 | 1.15 | 0.19 | 6.05 |
| Patient 4 | Primary | 5 | DENV-2 | 4 | 0.52 | 0.25 | - |
| Patient 5 | Primary | 5 | DENV-2 | 4 | 9.76 | 0.28 | 34.85 |
| Patient 6 | Secondary | 5 | DENV-3 | 4 | 3.75 | 6.80 | 0.55 |
| Patient 7 | Secondary | 4 | DENV-2 | 7 | 1.1 | 2.47 | 0.44 |
All samples are from AllMS, New Delhi. All samples were classified as severe disease (SD) at the time of admission.
By Pan Bio capture ELISA, assay cut off 1.1
By PanBio capture ELISA, assay cut off 2.2
Ratios were not calculated when IgM and IgG index values were below assay cut off.
Supplementary Material
Acknowledgements
This work was supported by National Institutes of Health grant no. ICIDR 1UO1A/115654; Department of Biotechnology (DBT), Government of India grant nos. BT/PR5132/MED/15/85/2012 and BT/PR8470/med/29/726/2013; and NIH-DBT Human Immunology Project Consortium grant no. AI090023. G. Medigeshi is supported by the Wellcome Trust-DBT India Alliance Intermediate fellowship (no. IA/S/14/1/501291). S. Kumar is supported by the DBT/Wellcome Trust India Alliance Early Career Fellowship grant no. IA/E/18/1/504307. The authors thank N. Khanna (International Centre for Genetic Engineering and Biotechnology (ICGEB)) for discussions, W. M. Orenstein (Emory Vaccine Center) for critical review of the manuscript, and S. Singh and A. Singh (ICGEB) for technical support.
Footnotes
Author contributions
M.S., S.F.A., R.V., S.M., A.R., V.P.V., A.M.A., S.K.K., R.L. and A.S. carried out patient recruitment and follow-up. C.A., H.A., P. Sharma, H.P., K.N., R.C.R., D.M., S.G., L.P., S.K.B., S.F.A., R.V., E.S.R., Y.M.C., P. Bhatnagar, P. Singh, M.K., K.D., S.K., K.G., K.S., P. Bajpai, G.P.S., P. Shah, A.K., T.Y., C.W.D., R. Antia and G.R.M. performed the experiments, analysis and interpretation. J.W., A.A., A.M.A., S.K.K., R. Ahmed, R.L., A.S., A.C. and K.M-K. were involved in study design, analysis and interpretation. C.A., H.A., R. Ahmed, R.L., A.S., A.C. and K.M-K. prepared the paper.
Competing interests
The authors declare no competing interests.
Peer review information Nature Medicine thanks Eng Eong Ooi and the other, anonymous, reviewer(s) for their contribution to the peer review of this work. Primary Handling Editor: Saheli Sadanand, in collaboration with the Nature Medicine team.
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Data availability
All the raw data analyzed are provided as source files in the main text and in the extended data material. Individual de-identified data for age, sex and clinical disease classification are provided as source data in the supplementary information. Source data are provided with this paper.
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Associated Data
This section collects any data citations, data availability statements, or supplementary materials included in this article.
Supplementary Materials
Data Availability Statement
All the raw data analyzed are provided as source files in the main text and in the extended data material. Individual de-identified data for age, sex and clinical disease classification are provided as source data in the supplementary information. Source data are provided with this paper.