West Nile Virus and a Safe Blood Supply

Attention News Desk: Press Release (for immediate release)
Michele Hyndman (650) 723-8237
Michelle Bussenius (650) 723-8270 or (650) 504-7973

Stanford, CALIFORNIA – Cases of West Nile Virus (WNV) are appearing throughout California. To date, 88 patients in the State have been diagnosed with the infection, including one in Santa Clara County and three in Contra Costa County. Area blood centers, including Stanford Blood Center, the Blood Centers of the Pacific, and the American Red Cross, have responded to the emergence of the virus by testing every unit of blood collected for the virus using tests being evaluated in clinical trials or recently cleared by the FDA.

West Nile Virus is an infection that is transmitted to humans via mosquitoes that have previously fed on birds that carry the disease. Most people infected with the virus have no symptoms. About 20 percent will develop mild flu-like symptoms such as fever, body aches, chills, and general tiredness. Rarely, symptoms of WNV infection can be severe, especially in the elderly, infants, and people who have weakened immune systems as a result of treatments for cancer or other diseases. Severe WNV infections can lead to encephalitis (an infection of the brain), meningitis (an infection of the membrane covering the brain), and paralysis.

The FDA encourages blood banks to utilize newly developed tests for WNV. All blood collected by area blood centers is tested for the virus using nucleic acid testing (NAT) that searches for the genetic material of the virus. This testing is typically performed on pooled samples of donated blood. Because the level of WNV infection in the blood is sometimes very low, testing of pooled donor samples can miss some infections. Therefore testing of individual donations would be best. In order to perform NAT testing on individual samples, highly sophisticated automated equipment is necessary. Currently, automated testing platforms are not yet approved by the FDA, but their use is permitted for WNV testing as part of clinical trials in which the test performance is closely monitored.

Since 2004, it has been Stanford Blood Center's policy to test all donors by individual WNV testing once cases of WNV appear in the area. Other area blood banks perform individual testing of donations from specific regions where WNV is active, and continue pooled testing of other donations.

All three area blood banks ensure the public that all available measures are being taken to maximize the safety of the blood supply. Everyone is encouraged to take preventative action against contracting the disease by wearing protective clothing, and using insect repellents containing DEET while in areas known to have mosquitoes.There is no risk of contracting WNV, or any other disease, through donating blood. Local blood banks remind people that WNV season coincides with the typical summer blood supply shortages-donations are down while transplant surgeries and traumas are on the increase during the summer months. Stanford Blood Center, the American Red Cross, and the Blood Centers of the Pacific urge people to contact their local blood donation center and save lives by donating blood today.


Stanford University Medical Center integrates research, medical education and patient care at its three institutions – Stanford University School of Medicine, Stanford Hospital & Clinics and Lucile Packard Children's Hospital at Stanford. For more information, please visit the Web site of the medical center's Office of Communication & Public Affairs at http://mednews.stanford.edu.