During the 2002 West Nile virus epidemic in the United States, patients were identified whose West Nile virus illness was temporally associated with the receipt of transfused blood and blood components.Patients with laboratory evidence of recent West Nile virus infection within four weeks after receipt of a blood component from a donor with viremia were considered to have a confirmed transfusion-related infection. We interviewed the donors of these components, asking them whether they had had symptoms compatible with the presence of a viral illness before or after their donation; blood specimens retained from the time of donation and collected at follow-up were tested for West Nile virus.Twenty-three patients were confirmed to have acquired West Nile virus through transfused leukoreduced and nonleukoreduced red cells, platelets, or fresh-frozen plasma. Of the 23 recipients, 10 (43 percent) were immunocompromised owing to transplantation or cancer and 8 (35 percent) were at least 70 years of age. Immunocompromised recipients tended to have longer incubation periods than nonimmunocompromised recipients and infected persons in mosquito-borne community outbreaks. Sixteen donors with evidence of viremia at donation were linked to the 23 infected recipients; of these donors, 9 reported viral symptoms before or after donation, 5 were asymptomatic, and 2 were lost to follow-up. Fever, new rash, and painful eyes were independently associated with being an implicated donor with viremia rather than a donor without viremia. All 16 donors were negative for West Nile virus-specific IgM antibody at donation.Transfused red cells, platelets, and fresh-frozen plasma can transmit West Nile virus. Screening of potential donors with the use of nucleic acid-based assays for West Nile virus may reduce this risk.

Transmission of West Nile Virus through Blood Transfusion in the United States in 2002