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Journal of Virus Eradication logoLink to Journal of Virus Eradication
. 2022 Jun 27;8(2):100077. doi: 10.1016/j.jve.2022.100077

Assessment of dengue virus threat to blood safety and community health: A single center study in northern Egypt☆

Ekram W Abd El-Wahab a,∗, Karima SR Elfiky b,c, Mohamed A Ghanem d, Hanan Z Shatat a
PMCID: PMC9251716  PMID: 35795869

Abstract

Background

The risk of transfusion transmitted dengue (DENV) is increasingly recognized and poses a risk to blood safety as well as spreading into non-immune communities.

Objectives

To determine dengue serological profile, environmental risk, knowledge, and preventive measures among blood donors in a national blood bank in northern Egypt.

Methods

A total of 500 blood donors were enrolled into this study between June and September 2018. Socio-demographic and medical data were collected using a predesigned questionnaire. Blood samples were screened for anti-DENV IgM, anti-DENV IgG and non-structural protein 1 antigen (DENV-NS1 antigen).

Results

History of past dengue exposure was identified in 10.2% of blood donors. No samples (0.0%) tested positive for anti-DENV IgG, IgM or NS1 antigen. At the time of blood donation, no individuals had any symptoms suggestive of a dengue-related illness. Dengue exposure strongly correlated with travel to the Kingdom of Saudi Arabia (KSA), Sudan and the El-Quseir outbreak area in Egypt. Knowledge of dengue and prevention methods was found to be substantially deficient, and the relatively higher level of knowledge among exposed donors did not translate into appropriate preventative measures.

Conclusions

Our risk assessment shows the impact of travel on DENV exposure and highlights its potential threat to disease spread in Egypt. Dengue awareness programs are urgently needed for effective prevention of transmission.

Keywords: Dengue, Screening, Blood donor, Risk, Knowledge, Practices, Egypt

1. Introduction

Dengue virus (DENV) infection is a major public health problem globally and endemic in more than 100 countries with an estimated 100 million infected cases and 25,000 deaths per year.1, 2, 3, 4, 5 Over the past few decades, DENV transmission has increased significantly around the globe with more than 2.5 billion people at risk of infection.3,5, 6, 7 Notable outbreaks of dengue fever (DF) in Egypt were reported in 1799, 1871, 1928, and 1937.8 Recently, the country has experienced an outbreak in 2015 in the Dayrout district of the Assiut Governorate.9 In 2017, a total of 110 people were confirmed to have DF in the Red Sea city of Quseir and the Qena governorate of Upper Egypt.10 Consequently, Egypt was recognized as having an intermediate probability of dengue infection on the global dengue map.3

Most commonly, DENV transmission occurs from the bite of an infected female Aedes aegypti mosquito (sometimes Aedes albopictus) with humans as the major amplifying host for the virus.4,7 During the viremic phase, dengue can become a blood-borne illness in both symptomatic and asymptomatic individuals.11 It is plausible that climatic change, rapid urbanization, population growth, increased international travel and breakdown of vector control measures have all greatly contributed to the recent disease emergence in Egypt.12 The vector has a known distribution in Egypt7 and the potential role of foreign visitors or Egyptians returning from neighboring African and Southeast Asian countries with known dengue endemicity is of great concern. Some of these visitors may arrive while viremic and, thereby facilitate DENV spread.

The prevention of and response to dengue infection and other arboviruses involve developing and implementing preparedness plans. So far, no dengue prevention and control programs have been put into place on a national scale by the Ministry of Health and Population (MoHP) in Egypt which require community participation. There have been no large-scale studies either to assess the current knowledge, attitudes and behaviors (KAB) about DENV transmission and its prevention conducted in Egypt.

Transfusion- and transplantation-associated dengue cases have been reported, and, although rare, still represent risks to the safety of blood products and transfusions. Asymptomatic blood donors in endemic areas may serve as potential vehicles of transmission which could be a serious source of virus dissemination in the wider community.11,13 The presence of anti-DENV antibodies is a further important cause of concern in transfusion medicine due to their immunogenic potential.14 However, mandatory screening of blood donors for dengue would be expensive in a developing country and should only be implemented after an evaluation of the risks posed by otherwise healthy blood donors. Blood banks in disease-endemic countries rely on verbal questioning to rule out the risk of transfusion-transmitted dengue, although this cannot rule out asymptomatic infection.11

Given the absence of an approved blood screening test for DENV in Egypt and in response to new epidemiological data, we would like to determine the seroprevalence of DENV antibodies among blood donors in a selected blood bank to assess the safety of blood donation services in Egypt. Evidence of exposure among blood donors would be useful for future implementation of immunization and blood screening policies. We have also assessed the KAP related to DENV and explored socio-demographic and environmental determinants of its exposure among blood donors.

Together, the present study could help to give an overview of the key parameters needed for preparedness planning, epidemic detection and emergency response for DENV containment and control tailored to the local context.

2. Methods

2.1. Study settings, design, and population

A cross-sectional study was conducted at the blood bank of Kafr El-Dawar General Hospital. Kafr El-Dawar is a rural city in the El-Behira governorate (31.14°N, 30.13°E) (Fig. 1). It has a population density of approximately 1385.8 inhabitants/km.2 Like many agricultural cities in the Nile delta, Kafr El-Dawar has experienced exceedingly rapid urbanization and economic activity.15

Fig. 1.

Fig. 1

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Map of Egypt showing the city of the study setting (yellow circle), cities that experienced dengue outbreaks in the past few years (red circles), and the capital of Egypt (green circle). Boundaries with dengue endemic neighboring countries are indicated by green dashed lines. (For interpretation of the references to colour in this figure legend, the reader is referred to the Web version of this article.)

The target population included blood donors attending the selected blood bank for blood donation.

2.2. Sampling

No data regarding the prevalence of DENV virus infection/exposure among blood donors in Egypt is available. However, the prevalence among the general population in some cities in Upper Egypt, where outbreaks of dengue have been previously reported, was found to be 12.09%.16 Using an alpha error = 5% and a precision = 3%, the minimum required sample size was found to be 454, and we eventually enrolled 500 participants. The sample size was calculated using Epi-Info software (version 7). Blood donors who had been accepted for blood donation according to the policy set up by the Egyptian Ministry of Health and Population, and who had agreed to participate in the study were enrolled consecutively until the required sample size was reached.

2.3. Data collection methods and tools

Investigators conducted in-person interviews using a predesigned structured questionnaire form17 (File S1). All serum samples were screened for anti-DENV antibodies [IgM-IgG] and DENV NS1 Ag (non-structural protein 1 antigen), using the Dengue Combo rapid diagnostic test (Biopanda Reagents, UK) to test for dengue viremia, active exposure, or previous exposure. The assay was performed according to the manufacturer's instructions. The status of blood borne viral exposure [hepatitis C (HCV) Ab, hepatitis B (HBV) surface antigen (HBsAg), and HIV Ab] was checked in all tested donors' samples as this is routinely done in all blood banks in Egypt after obtaining participants' consent.

2.4. Case definition

  • -

    Dengue exposure is defined by seroreactivity to anti-DENV IgG on a single immunoassay. This can be supported by history and/or a proven medical record of past dengue infection.

  • -

    Active dengue infection is defined by seroreactivity to DENV NS1 Ag and/or anti-DENV IgM (with or without anti-DENV IgG seroreactivity).

2.5. Statistical analysis

Collected data was reviewed for accuracy and completeness and analyzed using the Statistical Package for Social Sciences (IBM SPSS Statistics for Windows, Version 20.0, Armonk, NY: IBM Corp. Released 2011).

2.6. Scoring

Environmental risk, any knowledge of dengue and practices for dengue prevention were assessed using open-ended questions. Correct answers were scored 1 point, whereas wrong/“do not know” answers were scored with 0 point. Each outcome was computed as the sum of participant responses and categorized based on the modified Bloom's cut-off point. The total score was qualified as “high” if exceeding 75% of the total score, “average” for scores from 50% to 75% and low for scores below 50%.

3. Results

3.1. Characteristics of the study population

Study subjects were predominantly men (95.4%) with a median age of 32 years (range 18–50), rural residents (79.2%), and of low socioeconomic background (92.2%). Other socio-demographic characteristics are provided in Table 1. Donations were aimed at family members (directed donation).

Table 1.

Sociodemographic characteristics of the study participants.

Total (n=500)
 History of dengue exposure
 p
No (n=449)
 Yes (n=51)
No. % No. % No. %
Age categories 18 - <25 81 16.2 79 17.6 2 3.9 0.017
25 - <35 274 54.8 246 54.8 28 54.9
35–50 145 29.0 124 27.6 21 41.2
Mean ± SD. 32.1 ± 7.2 31.8 ± 7.3 34.3 ± 5.4 t= −3.0 p= 0.009
Sex Male 477 95.4 426 94.9 51 100.0 0.098
Female 23 4.6 23 5.1 0 0.0
Residence Urban 104 20.8 92 20.5 12 23.5 0.612
Rural 396 79.2 357 79.5 39 76.5
Period of residence <1 year 9 1.8 9 2.0 0 0.0 0.593
From 1 to 5 years 20 4.0 18 4.0 2 3.9
>5 years 471 94.2 422 94.0 49 96.1
Marital status Single 154 30.8 147 32.7 7 13.7 0.037
Married 342 68.4 298 66.4 44 86.3
Widowed 3 0.6 3 0.7 0 0.0
Divorced 1 0.2 1 0.2 0 0.0
Education Illiterate 27 5.4 27 6.0 0 0.0 0.002
Read and write 87 17.4 78 17.4 9 17.6
Primary school 58 11.6 57 12.7 1 2.0
Secondary (high) school 189 37.8 158 35.2 31 60.8
University education 139 27.8 129 28.7 10 19.6
Occupation Unemployed/ not working 136 27.2 132 29.4 4 7.8 <0.001
Farmer/ Agriculture work 49 9.8 47 10.5 2 3.9
Public sector worker 39 7.8 36 8.0 3 5.9
Professional job 59 11.8 52 11.6 7 13.7
Craft work 109 21.8 84 18.7 25 49.0
Retired 3 0.6 3 0.7 0 0.0
Student 62 12.4 60 13.4 2 3.9
Housewife 3 0.6 3 0.7 0 0.0
Auxiliary worker 40 8.0 32 7.1 8 15.7
Socioeconomic standarda Low (<21) 461 92.2 414 92.2 47 92.2 0.990
Middle (21–31.5) 39 7.8 35 7.8 4 7.8
Smoking Never 96 19.2 89 19.8 7 13.7 0.251
Current smoker 294 58.8 263 58.6 31 60.8
Ex-smokerb 16 3.2 16 3.6 0 0.0
Passive smoking 94 18.8 81 18.0 13 25.5
Smoking other than cigarettes Never 448 89.6 403 89.8 45 88.2 0.736
Yes, frequent (water pipe, shisha) 52 10.4 46 10.2 6 11.8
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SD: Standard deviation.

No history of alcohol intake or substance abuse was reported.

a: socioeconomic standard was calculated according to a scoring system developed by Fahmy and El-Sherbini.

b: includes smoker if quitted less than 1 year ago.

3.2. Serological profile of DENV infection

History of exposure to dengue was reported by 51 donors (10.2%), whereas anti-DENV IgG, anti-DENV IgM, and DENV NS1 Ag were not detected in any serum samples. At the time of blood donation, none of the donors showed symptoms consistent with the presence of dengue or other viral illness, although 8 (1.6%) and 1 (0.2%) were found seropositive for HCV and HBsAg antibodies, respectively (asymptomatic chronic cases). Likewise, none of the exposed donors had symptoms suggestive of dengue in the 3 months before the current blood donation, although all of them reported having had an episode of DF in the past (2016 to 2018) (Table 2).

Table 2.

Travel and medical history of the study participants.

Total (n=500)
 History of dengue exposure
 p
No (n=449)
 Yes (n=51)
No. % No. % No. %
Travel No 440 88.0 440 98.0 0 0.0 <0.001
Yes 60 12.0 9 2.0 51 100.0
Saudi Arabia 46 9.2 9 2.0 37 72.5
Sudan 1 0.2 0 0.0 1 2.0
Red Sea (Egypt)a 13 2.6 0 0.0 13 25.5
Year of travel 2016 17 3.4 2 22.2 15 29.4
2017 29 5.8 3 33.3 26 51.0
2018 14 2.8 4 44.4 10 19.6
History of mosquito bite in last 3 months No 216 43.2 174 38.8 42 82.4 0.001
Yes 284 56.8 275 61.2 9 17.6
History of vaccination in the past year No 498 99.6 447 99.6 51 100.0 0.001
Yes 2 0.4 2 0.4 0 0.0
Clinical symptoms in the past 3 monthsb Yes 166 33.2 160 35.6 6 11.8 0.001
Fever 14 2.8 13 2.9 1 2.0 0.701
Headache 150 30.0 145 32.4 5 9.8 0.001
Skin rash 3 0.6 3 0.7 0 0.0 0.558
Joint pain 5 1.0 5 1.1 0 0.0 0.449
Fatigue 20 4.0 18 4.0 2 3.9 0.976
Dizziness 2 0.4 2 0.4 0 0.0 0.633
Myalgia 19 3.8 19 4.2 0 0.0 0.134
Vomiting 7 1.4 6 1.3 1 2.0 0.719
Nausea 7 1.4 6 1.3 1 2.0 0.719
Abd pain 21 4.2 20 4.5 1 2.0 0.400
Dark urine 1 0.2 1 0.2 0 0.0 0.736
Loss of appetite 4 0.8 4 0.9 0 0.0 0.499
Altered consciousness 1 0.2 1 0.2 0 0.0 0.736
Serological profile of screened bloodborne viruses HCV 8 1.6 8 1.8 0 0.0 0.337
HBV 1 0.2 1 0.2 0 0.0 0.736
HIV 0 0.0 0 0.0 0 0.0 –
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a; a city in Egypt lying 500 km far from the city of study setting, and in which outbreaks of dengue fever were reported in 2016 and 2017.

b; No history of bleeding, conjunctival suffusion, chills, rigors, jaundice, eye pain, confusion, photophobia, or blurred vision was reported.

No history of hospitalization, major/minor operations, receiving blood or blood products, injections, Hijama (bloodletting), acupuncture, electrolysis, piercing, tattooing, injury, animal bite, abortion, or contact with blood in past 3 months was reported.

DENV exposure showed no significant association with either sex, residence, or socioeconomic background of donors. However, the increase of DENV seropositivity among potential blood donors, related significantly to travel history, working activity, and level of education (p < 0.05) (Table 1).

3.3. Environmental risk assessment

All exposed donors had a history of travel to dengue-endemic or outbreak areas (p < 0.001). The overall environmental risk score was categorized as average among 64.4% and low among 33.8% of the study participants with no significant difference between exposed and non-exposed donors. Housing conditions that favor insect breeding, particularly house flies and mosquitoes, were reported by most of the study participants (94.4%). The presence of stray animals in residential areas was common as well (94.2%). Conversely, the presence of animals including pets in households was negligible (5.0%).

Latrines predominately of ventilated improved pit (V.I.P) (58.8%) and aqua privy (41.0%) types were available in all households except for two (3.9%) of the exposed donors who reported having a pit latrine.

Wastewater was mainly disposed of through a municipal sewerage system (71.0%) or septic tank (29.0%). Solid waste was disposed of by the municipality (64.2%) and/or burned (45.6%), although most participants (97.0%) reported the presence of litter and garbage heaps in their neighborhood (Table 3) (Fig. 2).

Table 3.

Environmental risk assessment among the study population.

Total (n=500)
 History of dengue exposure
 p
No (n=449)
 Yes (n=51)
No. % No. % No. %
Travel to dengue endemic area Yes 60 12.0 9 2.0 51 100.0 <0.001
Shape of the house Apartment 484 96.8 436 97.1 48 94.1 0.251
Dwelling 16 3.2 13 2.9 3 5.9
Type of building material Red bricks 500 100.0 449 100.0 51 100.0 ND
Concrete 500 100.0 449 100.0 51 100.0
Presence of insects and rodents No 3 0.6 3 0.7 0 0.0 0.558
Yes 497 99.4 446 99.3 51 100.0
House flies 496 99.2 445 99.1 51 100.0 0.499
Mosquitos 495 99.0 444 98.9 51 100.0 0.449
Creeping insects (ants, cockroaches) 161 32.2 153 34.1 8 15.7 0.008
Rodents 3 0.6 2 0.4 1 2.0 0.184
Presence of stray animals in residential places No 29 5.8 25 5.6 4 7.8 0.510
Yes 471 94.2 424 94.4 47 92.2
Housing conditions favoring mosquito breeding No 3 0.6 3 0.7 0 0.0 0.558
Yes 497 99.4 446 99.3 51 100.0
Presence of peridomestic water containers 326 65.2 286 63.7 40 78.4 0.036
Having plants indoor 319 63.8 280 62.4 39 76.5 0.047
Having plants outdoor 485 97.0 435 96.9 50 98.0 0.646
Presence of a near-by water canal 399 79.8 357 79.5 42 82.4 0.632
Presence of near-by water collection sites 374 74.8 331 73.7 43 84.3 0.099
Presence of a near-by chocked sewage/drainage system 344 68.8 305 67.9 39 76.5 0.211
Presence of near-by garbage heaps 483 96.6 434 96.7 49 96.1 0.828
Availability of latrine in the house No 0 0.0 0 0.0 0 0.0 ND
Yes 500 100.0 449 100.0 51 100.0
Pit latrine 2 0.4 0 0.0 2 3.9 <0.001
V.I.P latrine 294 58.8 265 59.0 29 56.9 0.767
Aqua privy 205 41.0 184 41.0 21 41.2 0.978
Method of wastewater disposala Sewerage system 355 71.0 310 69.0 45 88.2 0.004
Septic tank 145 29.0 139 31.0 6 11.8 0.004
Method of solid waste disposal Scattered 485 97.0 434 96.7 51 100.0 0.185
Burning 228 45.6 214 47.7 14 27.5 0.006
Municipal 321 64.2 279 62.1 42 82.4 0.004
Presence of animals in household, including pets No 475 95.0 425 94.7 50 98.0 0.134
Yes 25 5.0 24 5.3 1 2.0
Cat 3 0.6 3 0.7 0 0.0 0.558
Dog 1 0.2 1 0.2 0 0.0 0.736
Cattle 23 4.6 22 4.9 1 2.0 0.342
Donkey 3 0.6 3 0.7 0 0.0 0.558
Sheep 3 0.6 3 0.7 0 0.0 0.558
Camel 19 3.8 19 4.2 0 0.0 0.134
Hoarse 2 0.4 2 0.4 0 0.0 0.633
Livestock bransb None 478 95.6 428 95.3 50 98.0 0.370
In the backyard 12 2.4 11 2.4 1 2.0 0.829
Far from house 10 2.0 10 2.2 0 0.0 0.282
Total environmental risk score 12.5±2.8 12.4±2.8 13.4±2.3 t= −1.93 p= 0.057
Low 169 33.8 157 35.0 12 23.5 0.130
Average 322 64.4 283 63.0 39 76.5
High 9 1.8 9 2.0 0 0.0
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a; no use of cesspool, trench, or open defecation was reported.

b; brans were not reported to be in the same household, or occupying the ground floor.

Fig. 2.

Fig. 2

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Photos from the city of the study setting showing local housing and roads, and outdoor environmental conditions favoring mosquito breeding [water canals, flooding, water collection sites, stagnant water ponds, chocked sewage/drainage system, garbage heaps and stray animals in residential areas].

3.4. Knowledge of dengue infection

The level of knowledge among study participants regarding dengue infection and transmission was mainly (94.4%) scored as low, although 52.9% of exposed donors achieved average knowledge scores (p < 0.001). Most exposed respondents were aware of the danger of mosquito bites (62.7%), knew dengue as a disease (90.2%), transmittable by mosquito bites (92.2%), and correctly identified some of the potential indoor and outdoor mosquito breeding sites (p < 0.001). The treating physician was the major source of information on dengue among the exposed participants (96.1%) (p < 0.001), although none of the respondents was aware that dengue could be contracted through blood transfusion (Table 4).

Table 4.

Knowledge of dengue infection among the study participants.

Total (n=500)
 History of dengue exposure
 p
No (n=449)
 Yes (n=51)
No. % No. d No. %
Awareness of danger of mosquito bite No 467 93.4 448 99.8 19 37.3 <0.001
Yes 33 6.6 1 0.2 32 62.7
Knowledge of diseases transmitted through mosquito bit No 452 90.4 448 99.8 4 7.8 <0.001
Yes 48 9.6 1 0.2 47 92.2
Malaria 18 3.6 0 0.0 18 35.3 <0.001
Dengue 48 9.6 1 0.2 47 92.2 <0.001
Yellow fever 1 0.2 0 0.0 1 2.0 0.003
Ever heard about dengue fever No 453 90.6 448 99.8 5 9.8 <0.001
Yes 47 9.4 1 0.2 46 90.2
know how dengue is transmitteda Do not know 451 90.2 448 99.8 3 5.9 <0.001
Mosquito bite 49 9.8 1 0.2 48 94.1 <0.001
Source of information NA 449 89.8 448 99.8 1 2.0 <0.001
Neighbors 5 1.0 0 0.0 5 9.8 <0.001
Treating physician 50 10.0 1 0.2 49 96.1 <0.001
Friends 19 3.8 0 0.0 19 37.3 <0.001
Family 1 0.2 0 0.0 1 2.0 0.003
Indoor mosquito breeding sites Do not know 469 93.8 447 99.6 22 43.1 <0.001
Garbage bin 30 6.0 2 0.4 28 54.9 <0.001
Plant container 22 4.4 1 0.2 21 41.2 <0.001
Kitchen/bathroom drain free 3 0.6 0 0.0 3 5.9 <0.001
Un covered water containers 19 3.8 0 0.0 19 37.3 <0.001
Water in trays under the fridge 8 1.6 0 0.0 8 15.7 <0.001
Flowerpot trays 11 2.2 0 0.0 11 21.6 <0.001
Outdoor mosquito breeding sites Do not know 470 94.0 447 99.6 23 45.1 <0.001
Garbage heaps 29 5.8 2 0.4 27 52.9 <0.001
Outdoor drains 2 0.4 1 0.2 1 2.0 0.062
Floor leaves 1 0.2 0 0.0 1 2.0 0.003
Un covered peridomestic water containers 21 4.2 1 0.2 20 39.2 <0.001
Nearby water canals 25 5.0 1 0.2 24 47.1 <0.001
Near-by stagnant water ponds 27 5.4 0 0.0 27 52.9 <0.001
Total knowledge score 1.0±3.3 0.04±0.64 9.53±4.82 t= −14.04 p <0.001
Low 472 94.4 448 99.8 24 47.1 <0.001
Average 28 5.6 1 0.2 27 52.9
High 0 0.0 0 0.0 0 0.0
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NA: not applicable.

ND: not determined.

a; Blood transfusion, unsafe injections, eating unclean vegetables, drinking unclean water, surgery, animal bite, flies, contact with rodents were not selected among responses to possible moods of dengue virus transmission.

3.5. Preventive measures against dengue

All participants showed unsatisfactory practices toward dengue prevention, although exposed donors demonstrated relatively better prevention practices compared to non-exposed ones (p= 0.010). When considering measures taken to prevent mosquito bites during travel, the use of repellents (17.4%) was almost the single action taken. Popular protective methods used in households included window screens (97.8%), repellents and mosquito coils (60.6%), and insecticides (28.6%). Most respondents (97.2%) reported that the authorities did take measures to prevent mosquito breeding, mainly through fogging outside the house, and a few experienced authority inspections of mosquito larvae in their neighborhoods. All participants had access to clean water and most of them stored water at home in refrigerators (99.2%). Responses about preventive practices to reduce indoor/outdoor mosquito breeding and mosquito-human contact included placing all garbage that can accumulate water into closed bins (91.8%), covering water containers in the home (75.4%), avoiding placing any water containers outdoors (75.0%), and removing water from trays under the fridge (15.4%) (Table 5).

Table 5.

Mosquito control measures adopted by the study participants.

Total (n=500)
 History of engue exposure
 p
No (n=449)
 Yes (n=51)
No. % No. d No. %
Measures taken to prevent mosquito bite while traveling? No 412 82.4 368 82.0 44 86.3 0.443
Yes 88 17.6 81 18.0 7 13.7
Repellents 87 17.4 81 18.0 6 11.8 0.263
Mosquito net 2 0.4 0 0.0 2 3.9 <0.001
Window screens 1 0.2 0 0.0 1 2.0 0.003
Stay indoor between dusk and dawn 1 0.2 0 0.0 1 2.0 0.003
Wearing long sleeves and pants 2 0.4 0 0.0 2 3.9 <0.001
Chemoprophylaxis 1 0.2 0 0.0 1 2.0 0.003
Measures taken to control mosquito/insects in households No 5 1.0 5 1.1 0 0.0 0.449
Yes 495 99.0 444 98.9 51 100.0
Insecticides 143 28.6 127 28.3 16 31.4 0.644
Repellents, coils 303 60.6 269 59.9 34 66.7 0.349
Window screens 489 97.8 440 98.0 49 96.1 0.376
Sleep under mosquito net 5 1.0 1 0.2 4 7.8 <0.001
Traps 2 0.4 0 0.0 2 3.9 <0.001
Measures done by health authority to control mosquitoes No 13 2.6 10 2.2 3 5.9 0.120
Yes 487 97.4 439 97.8 48 94.1
Inspection of mosquito larvae inside the house 0 0.0 0 0.0 0 0.0
Inspection of mosquito larvae outside the house 5 1.0 4 0.9 1 2.0 0.467
Fogging inside the house 0 0.0 0 0.0 0 0.0
Fogging outside the house 486 97.2 438 97.6 48 94.1 0.159
Put larvicidal in potentially breeding sites 0 0.0 0 0.0 0 0.0
Measures to prevent indoor/outdoor mosquito breeding No 39 7.8 35 7.8 4 7.8 0.990
Yes 461 92.2 414 92.2 47 92.2
Place all garbage that can accumulate water into closed bin 459 91.8 413 92.0 46 90.2 0.660
Change water in plant container 7 1.4 7 1.6 0 0.0 0.369
Keep drain free from blockage 7 1.4 7 1.6 0 0.0 0.369
Cover all water containers 377 75.4 333 74.2 44 86.3 0.057
Removing water in trays under the fridge 77 15.4 74 16.5 3 5.9 0.047
Remove water from flowerpot trays 3 0.6 2 0.4 1 2.0 0.184
Avoid placing any water containers outdoor 375 75.0 331 73.7 44 86.3 0.050
Avoid placing any unused tyres, cracked pots outdoor 27 5.4 24 5.3 3 5.9 0.872
Eliminating standing water around the house 0 0.0 0 0.0 0 0.0
Level defective floor surfaces that can collect water, if any 0 0.0 0 0.0 0 0.0
Adding larvicide in water containers 0 0.0 0 0.0 0 0.0
Method of water storage in households Water tank 4 0.8 4 0.9 0 0.0 0.499
Zeera 1 0.2 1 0.2 0 0.0 0.736
Refrigerator 496 99.2 445 99.1 51 100.0 0.499
Keeping water storage containers tightly closed Yes 432 86.4 384 85.5 48 94.1 0.090
Total practice score 9.6±1.8 9.6±1.8 10.0±1.2 t= −2.66 p= 0.010
Low 500 100.0 449 100.0 51 100.0 ND
Average 0 0.0 0 0.0 0 0.0
High 0 0.0 0 0.0 0 0.0
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A: a kind of large water jar made of pottery and used for drinking water storage in rural communities in Egypt.

3.6. Correlation between knowledge, practices, and environmental risk among study participants

The correlation of knowledge, practices and environmental risk scores overall revealed a significant positive correlation between knowledge and environmental risk (rs = 0.14, p = 0.003) and practice and environmental risk (rs = 0.46, p < 0.001), although the degree of correlation was fair (rs < 0.5). The correlation between knowledge and practice was remarkably low (rs = 0.06, p = 0.178) (Fig. 3).

Fig. 3.

Fig. 3

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A corrplot visualizing a correlation matrix of participant dengue-related knowledge, practices and environmental risk.

4. Discussion

Blood donors with asymptomatic dengue can contribute to the risk of transfusion-transmitted dengue. The Association for the Advancement of Blood & Biotherapies’ (AABB) Transfusion Transmitted Diseases Committee has categorized dengue as a high priority blood transmissible agent.18 However, transfusion-associated DENV is not recognized as a problem in Egypt given the relative scarcity of the disease. Screening of blood for this pathogen is costly and should be endorsed only after careful disease risk assessment.

Surveillance studies based on blood donors' donations have been used as an alternative strategy to estimate population prevalence by detecting circulating antibodies. Dengue seroprevalence screening has also been widely performed in blood donor samples in several studies worldwide (Table S1). No data on the seroprevalence of DENV among blood donors is available so far in Egypt. In the present study, we have assessed dengue seroprevalence among 500 blood donors in a rural city in northern Egypt. The detection of anti-dengue IgG antibodies in healthy donors is expected since IgG can persist over long periods compared to IgM.19 However, we were not able to detect anti-DENV IgG in the enrolled donors although almost 10% of them reported a history of exposure. This could be attributed to the poor sensitivity of the rapid test used. Indeed, the performance of some commercially available dengue rapid tests regarding real-time quantitative reverse transcription polymerase chain reaction and enzyme-linked immunosorbent assay results is quite low and their sensitivity can range from 40% to 60%.20

Testing of circulating DENV in healthy blood donors is crucial since transmission from blood transfusion is possible. All tested blood samples were seronegative for anti-DENV IgM and DENV-NS1 Ag. This allows to rule out most probably acute dengue infection. Indeed, given the small sample size, it was unlikely to be able to detect an acute/current DENV infection since there was no known dengue outbreak in the region at that time and donors infected in another country would probably have cleared the infection by the time they returned to Egypt and presented to donate blood. This can also reflect the effectiveness of pre-screening questionnaires, physical examination, and body temperature check of blood donors.

Our recorded DENV exposure rate is surprisingly high in a country with only occasional disease occurrence when considering the seroprevalence of dengue antibodies in blood donors of an endemic country/region which can be as high as 26.53%.21 Indeed, 10.2% of our donors had experienced some form of dengue infection several months before the study. Of the exposed donors, 75% had acquired dengue during their stay in KSA and one donor had contracted it in the Sudan, two countries of high disease endemicity. The remaining 25% of the exposed donors reported having had episodes of DF in 2017 during the dengue outbreak in El-Quseir,22 an industrial city in the Red Sea governorate in Egypt. This city has geographical proximity and traffic connections with KSA and the Sudan (Fig. 1), where this group of donors used to relocate for work.

Results from this study may reflect the exposure in adults since the median age of donors was 32. This is, however, expected to rise in numbers along with more adult samples. It is also difficult to correlate this set of data with the overall population because of a lack of samples from younger age groups (children and adolescents).

There might be an epidemiological link between the aforementioned dengue outbreaks in Egypt and endemic DENV infection in KSA. Indeed, Ae. aegypti and Ae. albopictus mosquitoes are both found in Egypt. However, DF is not endemic in the country, and for an outbreak to occur the virus must be introduced by viremic travelers, most probably from neighboring endemic countries. Given the established distribution of vectors in Egypt, there is a potential for dengue onward local transmission that might become established later as an endemic disease.

The lack of serological evidence of active dengue among donors was expected. However, this does not rule out the presence of asymptomatic active carriers who could transmit the virus to prospective recipients. Indeed, DENV-RNA can be detected in asymptomatic blood donors regardless of detectable levels of DENV specific antibodies, particularly in dengue endemic areas.23, 24, 25 Detection of viral RNA may not be achievable for routine large-scale screening in blood banks, particularly in low resource countries. Serological screening for the DENV-NS1 antigen is the alternative test for early diagnosis of asymptomatic DENV viremic donors.26

Detection of anti-DENV IgG in donor blood does not imply virus transmission to the recipients. However, the transmission of this class of antibodies may increase recipient's risk of developing serious forms of the disease, such as dengue hemorrhagic fever (DHF) and/or dengue shock syndrome (DSS)] upon infection with a different viral serotype. These cross-reactive heterotypic non-neutralizing and partially neutralizing antibodies can also enhance viral infectivity through antibody-dependent enhancement, which in turn has a negative impact on host innate immune responses.27, 28, 29 Prospective studies are warranted to assess the significance of this phenomenon in transfused subjects.

Transfusion of exposed blood with dengue specific antibodies may represent an additional threat to high-risk groups. Of concern are infants, young children, pregnant mothers, immunocompromised and chronic disease patients. The Egyptian population is highly burdened by a variety of liver diseases including hepatitis A,B and C as well as bilharziasis and fatty liver.30 Since hepatic dysfunction is a well-recognized feature of dengue,31 the transmission DENV or its cross-reactive antibodies through infected blood may cause serious disease in liver patients.

Dengue is a growing problem worldwide and increasingly reported among international travelers. In the present report, travel or even relocation to another city was strongly correlated with dengue exposure. Travelers returning from dengue endemic countries may offer to donate blood and since DENV can appear in the blood approximately 7 days before the appearance of symptoms,24 such asymptomatic carriers constitute a risk to blood safety. Hence, screening for DENV markers among blood donors with a recent travel history will strengthen blood transfusion safety and control disease dissemination and severity. Alternatives could be the deferral of blood donation for 6 months following return from a dengue endemic region or techniques such as pathogen inactivation.

Implementation of prevention and dengue control strategies require integrated epidemiological information to improve knowledge of factors related to local transmission. We have attempted in this study to address this aspect because the population in Egypt is at equal risk of contracting the infection from mosquito bites. Besides the presence of mosquito vectors, we have traced several environmental factors in the city of our study setting that together with limited vector and disease surveillance could facilitate sustained dengue transmission (Fig. 2). Due to the rapid urbanization of this rural community, there seems to be serious deficiencies in basic infrastructures and municipal services. This has resulted in the accumulation of garbage heaps in residential areas and water stagnation following flooding and stormwater which can turn into breeding ground for mosquitoes.

Despite the occurrence of several dengue outbreaks in Egypt, we have recorded a limited understanding of dengue among blood donors. Inadequate practices in preventing mosquito breeding have reflected this knowledge gap. The relatively higher level of awareness among exposed donors regarding dengue transmission and prevention methods did not, however, translate into effective preventative practices. Indeed, participant practices were not motivated by the awareness of the disease and its prevention but rather by mosquito nuisance. Thus, raising community awareness of dengue should receive more attention and support from health authorities.

Mass media plays a crucial role in conveying health information to the public.32,33 However, we found that the only source of dengue knowledge among study participants came from their health care providers (HCPs). Some studies have identified specific gaps in the knowledge about dengue prevention and management among HCPs that may reflect a lack of training.34,35Research and development of educational strategies to increase knowledge and practices of effective control measures among the general population are highly recommended. Employing mass and social media in this regard might be more effective in disseminating information and stress the community responsibility about its prevention.

In conclusion, potential blood donors can be exposed to DENV, as evidenced by their history of exposure. This warrants the integration of DENV screening into routine blood transfusion testing to ensure blood safety. Large community-based seroprevalence studies are required to estimate the true burden of infection in blood donors and the wider general population. Much remains to be done to fill up the gap in dengue knowledge and prevention practices. The present work constitutes the first step toward a better definition of DENV circulation in the Egyptian community and should help guiding preparedness plans and public health interventions to fight the infection. The present results are also important in terms of the national dengue awareness program in Egypt.

We recognize several limitations to this study including its relatively small sample size from only one blood bank. This might bring into question the inferred prevalence and limit the generalization of our research findings. Most participants were inevitably male because of the low proportion of women who donate blood in Egypt. Our screening approach was also limited by the absence of confirmatory testing. This is crucial particularly when there is a possibility of false-positive/negative results given the poor sensitivity of the rapid diagnostic test used. The use of enzyme-linked immunosorbent assay for antibodies or antigen determination would have been a better choice to test for DENV seroprevalence given its better sensitivity and specificity compared to the rapid test. We should have confirmed the results using real-time polymerase chain reaction as a reference method to eliminate false-negative results.

Ethical consideration

Ethical approval and consent to participate.

The study does not involve any work done on animals.

Conflicts of interest

All authors declare no conflicts of interest.

Consent for publication

All authors approved the manuscript for publication.

Availability of supporting data

All data are fully available without restriction by the corresponding author at ekram.wassim@alexu.edu.eg and through the public data repository http://www.opendatarepository.org/

Funding statement

Author own work. No funding or financial support was received.

Declaration of competing interest

The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.

Acknowledgements

We would like to acknowledge the study participants for accepting to participate in the study.

Footnotes

☆

The study was approved by the institutional review board and the ethics committee of the High Institute of Public Health affiliated with Alexandria University, Egypt. We sought the permission and support of the local health authorities to conduct the study in the selected districts in Alexandria. The study was conducted in accordance with the international ethical guidelines and of the Declaration of Helsinki. Informed written consent was obtained from each participant after explaining the aim and concerns of the study. Data sheets were coded by number to ensure anonymity and confidentiality of the participants' data.

Appendix A

Supplementary data to this article can be found online at https://doi.org/10.1016/j.jve.2022.100077.

Appendix A. Supplementary data

The following are the Supplementary data to this article:

Multimedia component 1
mmc1.docx (47.4KB, docx)
Multimedia component 2
mmc2.docx (50.5KB, docx)

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Associated Data

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

Supplementary Materials

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Data Availability Statement

All data are fully available without restriction by the corresponding author at ekram.wassim@alexu.edu.eg and through the public data repository http://www.opendatarepository.org/

Articles from Journal of Virus Eradication are provided here courtesy of Elsevier

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