A blood transfusion in 2008 has been linked to HIV transmission, the St. Louis Post-Dispatch reports. The last time this occurred was in 2002. According to the Centers for Disease Control and Prevention (CDC), a Missouri man donated blood during the approximately nine-day window after infection during which standard tests cannot spot the virus. The donor claimed during screening he had no risk factors for HIV despite his history of anonymous sexual encounters. A Colorado patient who received the man's blood later tested positive for HIV. The CDC estimates there is a 1 in 1.5 million chance of contracting HIV from a blood transfusion.

To read the Post-Dispatch story, click here.