West Nile and Blood Transfusions

A new study shows blood transfusions may have played a role in the spread of the West Nile virus during the 2002 epidemic in the United States.
Researchers interviewed individuals who donated their blood to patients infected with the West Nile virus. They asked the participants whether they had symptoms of a viral illness before or after donating the blood. Researchers also tested blood that was given at the time of donation and at a follow-up date for the West Nile virus.

Results of the study show 23 patients contracted the virus through a blood transfusion. Forty-three percent of those patients had weakened immune systems due to a previous transplantation or cancer, and 35 percent were age 70 or older and faced other medical challenges. Researchers say the virus took longer to fully develop in patients with weakened immune systems than in patients with normal immune systems.

The 23 patients with confirmed transfusion-related viruses were associated with 16 donors who had the presence of a virus in their blood. All of the donors tested negative for the West Nile virus antibody at the time of donation. However, nine of the donors reported viral symptoms, such as fever, rash, and pain in the eyes, before or after donating blood. Seven of the 16 donors were linked to two or three patients who contracted the West Nile virus.

Researchers say their findings may underrepresent the number of transfusion-related West Nile cases. They say testing donors with nucleic acid-based assays for the West Nile virus could reduce the risk of infection.