More than 1,000 blood donors have tested positive for West Nile virus in the United States, the Centers for Disease Control and Prevention (CDC) reported. West Nile virus, which usually is transmitted when a mosquito feeds on an infected bird, then bites a human, is now one of the most common pathogens transmitted through transfusions.
Lyle R. Petersen, MD, an expert on West Nile virus for the CDC, said that new screening tests introduced last summer have been effective at identifying infected blood donations. Several manufacturers are currently working to develop screening tests that are better at detecting the low levels of virus usually present in infected blood. Dr. Petersen made the comments while attending the annual meeting of the American Mosquito Control Association in Savannah, Ga.
About 2 dozen Americans became infected with West Nile virus via transfusion in 2002. Two of them developed West Nile encephalitis, one of the more serious complications of West Nile virus infection.
In 2003, a total of about 9,000 people contracted West Nile virus in the United States, and 230 people died from the infection. The only states that didn't report any human cases of West Nile virus last year were Alaska, Hawaii, Oregon, and Washington. Health officials expect the virus to continue spreading this summer.