With the spread of Zika virus (ZIKV) infection in the Americas there is the possibility that transmission via blood transfusions may have occurred, with some cases seen in Brazil. Preemptive testing of blood donations for ZIKV RNA was therefore implemented in southern US states that are thought to be at risk of local transmission using a test approved under a Food and Drug Administration (FDA) investigational new drug application, cobas Zika. The screening was then expanded following updated FDA guidance. Any donations found to be reactive on initial screening were further tested by nucleic acid and antibody tests to determine the donor status. Altogether, 358,786 donations from US states were screened by individual donation testing and 23 of these were found to be initially reactive on cobas Zika. 14 of these 23 were probable ZIKV infection, based on results from additional nucleic acid testing or anti-Zika IgM. Ten of the 14 donors reported travel to an identified ZIKV-active area in the previous 90 days (median time from end of travel to donation 25 days, range 6–71 days). Three of these donors with a travel history also reported potential sexual exposure. Only seven of the 14 donations with probable ZIKV infection could still be detected following 1:6 dilutions to simulate standard minipool testing. The estimated specificity of the cobas Zika test was 99.997%. Therefore screening for ZIKV RNA can identify potentially infected donors, especially those with risk factors such as travel and sexual exposure. Worryingly, minipool screening would have detected only 50% of the RNA-positive donations.
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