Blood donation and West Nile Virus Infection

In 2002, there were at least 23 confirmed cases of West Nile Virus (WNV) infection in the U.S. from transfusions and an estimated 500 donations by infected donors who did not have symptoms of infection. In 2003, blood collection facilities began screening donated blood using nucleic acid amplification tests (NATs); confirmed positive units are discarded.

Hundreds of donors whose donated blood tests positive when screened for the presence of West Nile Virus are identified each year in the United States. These donors are followed up by the blood agency to confirm their infection with additional tests and by the local health departments to see if they later go on to develop symptoms of WNV infection.

Licensed blood collection agencies in California have been requested to report any donors who test positive to the local health department. If you have been diagnosed with or develop symptoms compatible with West Nile Fever or West Nile Neuroinvasive Disease (see and you donated blood in the 14 days before your illness began please tell your doctor and notify your blood collection agency immediately. Physicians and laboratories should report West Nile Virus infection within one working day by phone to 714-834-8180 or by fax to 714-834-8196.

For more information on West Nile Virus infection and blood or organ donation, see