SEPT. 3–ATLANTA–Public health officials are assuring Americans that the blood supply was safe despite concerns that an organ donor who received a transfusion may have transmitted West Nile virus to four transplant recipients.

One of the four died of brain swelling that can be caused by the virus, which until now has been blamed solely on mosquito bites, according to the U.S. Food and Drug Administration (FDA).

The three others were hospitalized with symptoms associated with West Nile, although doctors aren’t sure they have the virus or whether they got it from a medical procedure.

The organ donor, a Georgia woman, died in a car crash last month. She may already have been infected or may have gotten West Nile through blood transfusions in the emergency room after the crash, the FDA’s Centers for Disease Control reports.

Samples from the four transplant recipients were sent to the CDC’s lab in Fort Collins, CO. Test results are expected within the week. The organ recipient who died was in the Atlanta area. The others are at hospitals in the Atlanta area, in Miami and Jacksonville, Fla., health officials said.

Public health officials spent the weekend assuring people about the national blood supply, despite the lack of a West Nile screening process in donated blood and organs. Any potential blood donor showing symptoms of the virus would be turned away, they say.

“The blood supply is as safe as it’s ever been,” Trudy Sullivan, an American Red Cross spokeswoman in Washington, told The Associated Press.

The FDA issued an alert to blood banks two weeks ago to exercise extra caution when screening donors.

“We’ve known for some time that there is a theoretical possibility that people can get this through blood or organ transplants,” says Tom Skinner, a CDC spokesman.

So far this year, 638 people in 27 states and the District of Columbia have tested positive for West Nile virus, and 31 have died.