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.