Dengue RNA detection and seroprevalence in blood donors during an outbreak in the São Paulo State, Brazil, 2016.

Most dengue virus (DENV) infections remain asymptomatic. This increases the risk of DENV transfusion transmission (TT-DENV) during outbreaks. We evaluated DENV viremia in 8475 blood donations assembled in minipools for the presence of DENV RNA. The tested samples were obtained between February and May, 2016, during a large DENV outbreak in Ribeirão Preto city, northeast region of the São Paulo State, Brazil. The DENV RNA + samples were serotyped and screened for DENV NS1. We also tested a significant number of plasma samples (n = 372) to estimate the DENV seroprevalence among blood donors in the region. We detected three DENV RNA + samples in the tested blood donations (n = 3/8475, 0.04%). From these, two samples were further serotyped as DENV-1 and one sample as DENV-2. All DENV RNA positive samples were negative for anti-DENV IgG, indicating the presence of primary acute infection. Moreover, two of the DENV RNA + samples were also NS1 antigen positive (antigenemia). The anti-DENV IgG seroprevalence among blood donor population was 50.8% (n = 189/372). Our results are in accordance with the presence of DENV primary infection in blood donors which can lead to transfusion transmission of the infection to recipients. Measures to exclude such donors should be adopted to prevent TT-DENV.

Zika virus RNA detection in asymptomatic blood donors during an outbreak in the northeast region of São Paulo State, Brazil, 2016.

BACKGROUND: In 2015, there was a large Zika virus (ZIKV) outbreak in Brazil. The proportion of asymptomatic infections is very high, and it is possible for transfusion-transmitted ZIKV (TT-ZIKV) infection to occur. The prevalence of asymptomatic ZIKV infection among Brazilian blood donors during this epidemic outbreak is unknown. STUDY DESIGN AND METHODS: Plasma samples obtained between October 2015 and May 2016 from 1393 volunteer blood donors were tested for ZIKV RNA. The viral load was quantified using an in-house standard curve. Additionally, positive ZIKV RNA samples were tested for anti-ZIKV immunoglobulin (Ig)M and anti-ZIKV IgG. RESULTS: Of the 1393 blood samples, ZIKV RNA was detected in 37 (n = 37/1393; 2.7%). The median infection viral load detected was 7714 copies/mL (ranging from 135-124,220 copies/mL). The majority of the positive samples (70.3%) exhibited a viral load of approximately 103 copies/mL. Six samples that were positive for ZIKV RNA were also positive for anti-ZIKV IgM and IgG (n = 6/37; 13.5%). CONCLUSION: This is the first study evaluating the prevalence of ZIKV RNA among Brazilian blood donors, which was relatively high and might lead to TT-ZIKV infection. It is unclear whether the simultaneous presence of anti-ZIKV IgM and IgG in RNA-positive donations or the viral load influences transfusion transmission of the infection. This study also adds to the global understanding of ZIKV prevalence in blood donors during outbreaks and the transfusion impact of the infection.