WASHINGTON, Sept. 5 (UPI) -- A fourth person who received an organ transplant has tested positive for West Nile virus and federal health officials are investigating whether a woman in Mississippi contracted the disease through a blood transfusion, the Centers for Disease Control and Prevention said Thursday.
The evidence is mounting that the disease -- which was thought to be transmitted only via mosquitoes -- can be spread by organ donations from infected people, CDC officials said. Even as they investigate the Mississippi case, however, they stressed there is no evidence at this time to suggest West Nile can be transmitted via blood transfusions.
Monday the CDC said three people who had received organ transplants from a Georgia woman, who had died in an automobile accident, developed the disease. The fourth person, announced Thursday, is a 71-year-old female who was released from the hospital and is recuperating at home in Jacksonville, Fla. She has a mild form of the disease and not the life-threatening brain infection that has killed 43 people so far this year, including one of the organ transplant recipients.
"Evidence very strongly suggests that these transmissions occurred via organ transplantation," Lyle Peterson, deputy director for the CDC's Division of Vector-Born Infectious Diseases, said during a teleconference with reporters. "I do not think that a mosquito bite is very likely at this time."
Officials still are not sure how the original organ donor contracted the virus, as she apparently was not exposed to mosquitoes. They continue to investigate the case and Peterson said, "It is most likely that the donor became infected with the West Nile virus through a mosquito bite or via blood transfusion shortly before organ donation."
Officials have taken the precaution of recalling the remaining blood products from batches that could have infected the original organ donor. But Peterson stressed, "There is absolutely no proof at this point that West Nile virus transmission by blood has occurred."
The CDC noted, however, it has recalled 18 units of blood products that potentially could have infected the Mississippi woman. Officials declined to give any details other than the woman developed West Nile infection after receiving multiple blood transfusions during gynecological surgery. The woman developed symptoms within the time frame consistent with contracting it from the blood transfusion, but Ed Thompson, Mississippi state health officer, noted she also reported multiple mosquito bites prior to being hospitalized.
It is just as likely she acquired the disease from mosquitoes as through tainted blood, Thompson said.
Officials maintained patients should not forego blood transfusions or organ transplantation procedures out of concern of contracting West Nile virus.
"The medical benefit of getting blood or organs far outweighs any risk of West Nile virus transmission," Peterson said. "If a person has a medical need for blood transfusion or a donated organ, they need that blood and they need that organ and West Nile virus transmission by this route is very rare and probably not very common."
Jesse Goodman, deputy director of Food and Drug Administration's Center for Biologics, Evaluation and Research, said a review by experts suggested procedures already in place for inactivating viruses in blood should destroy viruses very similar to West Nile. He added the agency will take a closer look at whether these inactivation procedures do in fact render West Nile harmless.
Goodman also noted blood donation centers screen people for fever or other symptoms that would indicate they are infected with West Nile virus and bar them from donating. That alone should remove most infected donors from the blood supply because the virus does not appear to persist in the blood once a person recovers from infection, he said.
Peterson noted that once a person becomes infected with West Nile they should be immune to it for a very long time, although it still is uncertain if that lasts for the life of the individual.
The CDC also reported more than 100 new cases of West Nile infection, bringing the national total to 854 and 43 deaths.
Peterson said, "CDC expects many more cases of West Nile Virus infection to be reported in the coming weeks as the transmission season peaks in different parts of the country."
