The fourth, a Florida woman aged 71, underwent a liver transplantation at a Jacksonville hospital then developed mild symptoms of viral infection without encephalitis. She tested positive for the virus at the Florida Department of Health laboratory and is now recovering at home. The donor, who died in Georgia on 1 August, was injured in a car crash and had several blood transfusions before she died. She was not known to have been ill before the crash, and a sample of her blood taken before she had any transfusions showed no evidence of West Nile virus. Dr Julie Geberding, director of the Centers for Disease Control and Prevention (CDC) in

Atlanta said on 30 August that “transmission of the West Nile virus through blood and organs is biologically plausible.” The CDC does not know whether the source of infection was mosquito bites or blood transfusions and is conducting further tests. It is also investigating a case diagnosed in a Mississippi resident nearly four weeks after the patient underwent a surgical procedure and received several units of blood. The patient reported having been bitten by mosquitoes on numerous occasions before being admitted to hospital. Donors of blood given to this patient are being contacted so they can be tested for the virus. Similarly, other recipients of blood components from these donors will also be contacted and tested.