First Zika-positive donations in the continental United States

Zika virus (ZIKV) has spread in the Americas, including parts of the southern United States, and infection can be associated with serious complications, including congenital brain abnormalities. Probable transfusion transmission of ZIKV has been documented in Brazil.

Preemptive testing of blood donations for ZIKV RNA was implemented in southern US states at risk of local transmission using a test approved under a Food and Drug Administration (FDA) investigational new drug application, cobas Zika. Screening was expanded after issuance of an updated FDA guidance. Donations reactive on initial screening were further tested by nucleic acid and antibody tests to determine the donor status.

Of 358,786 donations from US states screened by individual donation testing, 23 were initially reactive on cobas Zika. Fourteen of these represented probable ZIKV infection based on reactivity on additional nucleic acid testing or anti-Zika immunoglobulin M. Ten of the 14 donors reported travel to an identified ZIKV-active area within 90 days before donation (median time from end of travel to donation, 25 days; range, 6-71 days). Three donors with travel history also had a potential sexual exposure. Only seven of the 14 donations with probable ZIKV infection were detectable upon 1:6 dilution to simulate minipool testing. The estimated specificity of the cobas Zika test was 99.997%.

Screening of donations for ZIKV RNA can interdict ZIKV-infected donors. Donor risk factors include travel more than 4 weeks before donation and sexual exposure. Minipool screening would have detected only 50% of the RNA-positive donations.