The death of a transplant patient last week and illnesses in three other patients who received organ donations from the same donor in Georgia may prove to discredit what is known of the West Nile virus and how it is transmitted.

Further testing by the Centers for Disease Control in Atlanta may confirm the first instance of human-to-human transmission of West Nile virus. The virus is typically transmitted to humans through mosquitoes.

"Although transmission of the West Nile virus via blood transfusion or organ donation has been a theoretical possibility, transmission via these routes has not been previously observed," the CDC said in a statement Sunday.

The organs of an infected Georgia woman, who died last month in a car accident, were implanted in the four patients in early August. Before her death, she had received blood from 37 transfusions, raising the possibility that the woman had received infected blood; however, the chances are "very low," the CDC said.

The remaining blood from the 37 blood donors was recalled.

Encephalitis, which is caused by West Nile virus, was the confirmed cause of death in an autopsy of the transplant patient. Two others remain hospitalized with neurological illnesses, and the fourth organ recipient is recovering at home after developing fevers.

Robertson Davenport, medical director of Blood Bank and Transfusion Services in the University of Michigan Department of Pathology, said no test currently exists to detect West Nile virus during blood screenings.

Despite the small possibility of receiving infected blood, Davenport said no immediate changes will be made to donor screening procedures, as any potential donors who have received mosquito bites will not be turned away.

"Deferring people in that way would be more of a negative impact on the blood supply," he said.

Washtenaw County American Red Cross spokeswoman Pamela Reading-Smith said the blood donation program will not change its protocol for blood donor screening at this time.

"We are working intensely with the (Food and Drug Administration) and the CDC to get this situation straightened out."