FDA has approved a test that can detect West Nile Virus in donated human blood and plasma. Manufactured by Roche Diagnostics, the test is onlyÂ one of two on the market that can screen donated blood for the virus. Although most infections are spread via the bite of an infected mosquito, the first transfusion-transmitted infection of the virus was detected in 2003, according to Roche. Most people infected with West Nile don't get sick either or only have mild symptoms. One advantage to theÂ Cobas TaqScreen West Nile Virus Test is that it can detect the virus earlier in the infection cycle in donors who might not show any symptoms. A similar test made by Gen-Probe Inc. (San Diego)Â was cleared byÂ FDA in 2005.