Blood transfusions

Transfusion-associated transmission (TAT) of West Nile virus was first recognized in the United States, in 2002.  This prompted the rapid development of two nucleic acid testing (NAT) assays to screen donated blood for WNV viremia.  By July 14, 2004, all blood banks in the United States had implemented testing. 

FDA recommends screening year-round for WNV using a licensed minipool nucleic acid-amplification testing (MP-NAT) or individual donation NAT (ID-NAT) on donor samples of whole blood and blood components (FDA 2008). Because of the dilution effect inherent in screening by MP-NAT, this method is less sensitive than ID-NAT. FDA further recommends that blood centers using MP-NAT screening establish criteria to switch to ID-NAT during periods of high WNV activity in their geographic area of collection.

Frequently Asked Questions (CDC)

Instant feedback:

Since WNV-NAT testing was instituted to check all blood in July, 2004, the blood supply is completely safe from WNV.


CDC. West Nile Virus Home. Frequently Asked Questions. Retreived 11/3/17.

Food and Drug Administration. Guidance for industry: use of nucleic acid tests to reduce the risk of transmission of West Nile virus from donors of whole blood and blood components intended for transfusion. Rockville, MD: US Department of Health and Human Services, Food and Drug Administration; 2008.