Since October 2013, French Polynesia has experienced the largest documented outbreak of Zika virus (ZIKAV) infection. To prevent transmission of ZIKAV by blood transfusion, specific nucleic acid testing of blood donors was implemented. From November 2013 to February 2014: 42 (3%) of 1,505 blood donors, although asymptomatic at the time of blood donation, were found positive for ZIKAV by PCR. Our results serve to alert blood safety authorities about the risk of post-transfusion Zika fever.

BACKGROUND Zika virus (ZIKV) is an arthropod‐borne virus (arbovirus) transmitted by mosquitoes. The potential for ZIKV transmission through blood transfusion was demonstrated during the ZIKV outbreak that occurred in French Polynesia from October 2013 to April 2014. Pathogen inactivation of blood products is a proactive strategy that provides the potential to reduce transfusion‐transmitted diseases. Inactivation of arboviruses by amotosalen and ultraviolet A (UVA) illumination was previously demonstrated for chikungunya, West Nile, and dengue viruses. We report here the efficiency of this process for ZIKV inactivation of human plasma. STUDY DESIGN AND METHODS Plasma units were spiked with ZIKV. Viral titers and RNA loads were measured in plasma before and after amotosalen and UVA photochemical treatment. RESULTS The mean ZIKV titers and RNA loads in plasma before inactivation were respectively 6.57 log TCID50/mL and 10.25 log copies/mL. After inactivation, the mean ZIKV RNA loads was 9.51 log copies/mL, but cell cultures inoculated with inactivated plasma did not result in infected cells and did not produce any replicative virus after one passage, nor detectable viral RNA from the second passage. CONCLUSION In this study we demonstrate that amotosalen combined with UVA light inactivates ZIKV in fresh‐frozen plasma. This inactivation process is of particular interest to prevent plasma transfusion‐transmitted ZIKV infections in areas such as French Polynesia, where several arboviruses are cocirculating.

These results corroborate the expected high transmission of DENV and conversely suggest that no active circulation of ZIKV, JEV, and WNV occurred in French Polynesia before 2011. Information provided by this study may be useful for public health authorities to improve surveillance and implement strategies to prevent the transmission of arboviruses.

We report here that amotosalen combined with UVA light inactivated DENV in fresh-frozen plasma (5.61 log inactivation of viral titer). This inactivation process is an efficient method to prevent plasma transfusion-transmitted DENV infections.

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