Detection of West Nile virus in blood donations--Puerto Rico, 2007.

In the United States, West Nile virus (WNV) was first detected in humans in 1999; it subsequently spread to countries of Central and South America and the Caribbean. WNV is a mosquito-borne virus that produces potentially serious clinical disease, particularly among persons aged > or =50 years. Transmission by routes other than mosquito bites, including blood transfusion, transplacental infection, organ transplant, and possibly breast milk, also have been reported. On July 19, 2007, the American Red Cross in Puerto Rico notified the Puerto Rico Department of Health (PRDH) of three persons whose blood donations were positive for WNV by nucleic acid-amplification test (NAT) screening. These three donors had the first confirmed human WNV infections detected in Puerto Rico. In response, PRDH and CDC conducted in-depth interviews of the blood donors. This report describes these human infections and other recent surveillance for transmission of WNV in Puerto Rico. Detection of WNV infections in human blood donors indicates that heightened clinician awareness, ongoing surveillance, and educational activities are needed to monitor and assess the public health threat posed by WNV in Puerto Rico.