West Nile virus infection in blood donors in the New York City area during the 2010 seasonal epidemic.

BACKGROUND

A uniform threshold strategy for converting from minipool (MP)-nucleic acid testing (NAT) to individual donation (ID)-NAT screening for acute West Nile virus (WNV) infection among blood donors is lacking. We report on WNV screening at the New York Blood Center during the 2010 seasonal WNV epidemic, the most severe epidemic in that state since the original outbreak in 1999.

STUDY DESIGN AND METHODS

Between July 1 and October 31, 2010, blood donations were screened by MP-NAT or ID-NAT and the presence of anti-WNV immunoglobulin (Ig)M and IgG was evaluated among NAT-positive donations.

RESULTS

Twenty presumed viremic donations were identified for a frequency of 0.0129% (1 in 7752 donations). Nine donations that could have been missed by MP-NAT were identified. Two of these donations were both IgM and IgG negative, one of which would have been missed if more than one positive donation was required for initiating ID-NAT. Retrospective ID-NAT revealed two positive donations. The majority of the NAT-positive donations in New York (16/19) were from donors who lived in counties that had the highest incidence of human WNV cases in the state.

CONCLUSION

Our data details the identification of WNV NAT-positive blood donations during a severe seasonal epidemic in the New York area. By initiating ID-NAT after one positive donation, using retrospective testing, and triggering ID-NAT regionally, we were able to prevent the release of presumably infectious donations. The detection of NAT-positive donations with retrospective testing, however, may indicate the need for changes in our trigger criteria.