Seroprevalence of dengue among blood donors in Dar es salaam

Abstract

Background: During dengue outbreaks, only symptomatic individuals are screened for dengue infection. However, 75% of all adults infected with dengue virus are asymptomatic and may remain viraemic for up to a week. This increases the risk of transfusion-transmitted dengue if these individuals are asked to donate blood. Objective: To assess seroprevalence of dengue among blood donors during epidemics. Methodology: This was a cross sectional study that involved healthy voluntary blood donors. Serum samples were collected and screened for dengue specific antibodies and NS1 antigen using Dengue IgM, IgG+ Ns1 Combo rapid assays. Real time polymerase chain reaction (RT-PCR) was used to confirm active dengue infection among IgM and NS1 positive blood donors. A structured questionnaire was used to collect socio-demographic, environmental and clinical information. Binary logistic regression was used to identify factors associated with dengue seroprevalence. A two sided p-value <0.05 was considered statistically significant. Results: A total of 421 blood donors were enrolled into the study. The mean age of study participants was 32 ± 10 years, and majorities were males 368/421 (87.4%). The proportion of blood donors with recent exposure to dengue virus (DENV) was low, anti-DENV IgM was detected in 13/421 (3.1%) participants. A quarter of blood donors were previously exposed to DENV, 114/421 (27.1%) of them had anti-DENV IgG antibodies. NS1 antigen was not detected in any of the blood donors, and none of the IgM positive participants had DENV RNA. After adjusted analyses, only age below 30 years was found to be an independent predictor of IgG seroprevalence among blood donors. The odds of previous exposure to dengue were 30% higher among younger blood donors than in participants older than 30 years of age, OR= 1.30 (95% CI; 1.2-5.8), p=0.002. Conclusion: We found no evidence of viraemia or active dengue infection among blood donors during the 2019 outbreak in Dar es Salaam. The likelihood of transfusion transmitted dengue during epidemics in non-endemic regions is low. There fore it is not compulsory to carry out routine screening of blood donors for DENV virus during epidemics.