Chiron Corporation Release: PROCLEIX(R) West Nile Virus Assay Receives FDA Approval; New System Further Ensures Safety Of Blood Supply

EMERYVILLE, Calif.--(BUSINESS WIRE)--Dec. 1, 2005--Chiron Corporation (NASDAQ:CHIR) today announced that the U.S. Food and Drug Administration (FDA) has approved the PROCLEIX(R) West Nile Virus (WNV) Assay to screen whole blood donations for use on the PROCLEIX(R) System. The assay, which was developed in collaboration with Gen-Probe Incorporated, has been used to screen more than 29 million units of blood on an investigational-use-only basis since June of 2003 and intercepted more than 1,500 WNV-positive donations.