BACKGROUND: Southern Taiwan experienced a severe dengue epidemic in 2015. Adult asymptomatic cases would raise concerns on transfusion-transmitted dengue virus (DENV) infection. The aim of this study was to evaluate the magnitude of such a risk in Tainan City during this epidemic. STUDY DESIGN AND METHODS: The daily prevalence of asymptomatic dengue viremia in blood donors in Tainan City and in selected high-incidence districts during the 2015 dengue epidemic was estimated by an established mathematical model. Duration of viremia, duration of viremia before symptom onset, apparent-to-inapparent infection ratio, and reporting-to-underreporting ratio were four main parameters used in the model. RESULTS: The estimated maximal and mean daily prevalence of asymptomatic dengue viremia in blood donors in Tainan during this dengue epidemic was 74.4 (95% confidence interval [CI], 60.8-88.0) and 15.0 (95% CI, 12.3-17.7) per 10,000, respectively. In the district with the highest incidence, the maximal and mean daily prevalence of asymptomatic viremia was 328.8 (95% CI, 271.1-386.2) and 55.3 (95% CI, 43.4-63.3) per 10,000, respectively. Approximately 234 (95% CI, 191-276) blood components containing DENV were produced during the epidemic. CONCLUSION: Although dengue is currently not endemic in Taiwan, physicians need to be aware of the risk of transfusion-transmitted DENV infection. Our results suggest that screening measures to ensure blood safety should be evaluated and implemented during dengue epidemics even in nonendemic areas. Timely estimation of daily asymptomatic viremia prevalence by districts can help to select high-risk areas for such measures and to evaluate cost-effectiveness.
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