West Nile from Blood Transfusion Still Possible

Recently implemented blood screening rules have helped prevent many transfusion-related cases of West Nile virus (WNV) infection, but a small risk of such infection still exists, the US Centers for Disease Control and Prevention reported on Thursday.

Recently implemented blood screening rules have helped prevent many transfusion-related cases of West Nile virus (WNV) infection, but a small risk of such infection still exists, the US Centers for Disease Control and Prevention reported on Thursday. For this reason, screening changes are planned for 2004. In June 2003, testing for WNV was started to identify and eliminate blood donations at risk for carrying the virus. From June through December, approximately 6 million units were tested, resulting in the removal of more than 800 donations from the blood supply. Still, some transfusion-related cases did occur, apparently because low levels of virus were not detected by the testing. Twenty-three suspected cases of West Nile from transfusions were reported to the CDC last year, according to an article in the CDC’s Morbidity and Mortality Weekly Report. Of these cases, six were ultimately classified as confirmed or probable transfusion-associated WNV. In all of the cases, the recipient received components from multiple donations. However, in each case, only one component was found to be infectious, the CDC notes. None of these components showed evidence of WNV on initial screening. The current screening policy has definitely helped prevent transfusion-associated WNV infections, the CDC states. However, “documentation of the six WNV transfusion-associated transmission cases in 2003 indicates that blood components containing low levels of virus might escape detection and that at least some of these might be infectious.” Data from 2003 will help the blood banks and public health authorities come up with improved screening strategies for 2004, the report indicates. SOURCE: Morbidity and Mortality Weekly Report, April 9 2004.(Source: Reuters Health, April 2004)