CDC: West Nile threat to blood supply 'very low'
ATLANTA, Georgia (CNN) -- Federal health authorities are investigating whether the West Nile virus has been transmitted through blood transfusions or organ donations -- but they insist the nation's blood supply is safe.
Doctors with the Centers for Disease Control and Prevention said Sunday they were looking into an outbreak of illness in four patients who received organs from a single donor.
One of the transplant patients has died and another has tested positive for the West Nile virus. Two others have become ill and are awaiting the results of further tests, according to Dr. James Hughes, an infectious disease expert at the Atlanta-based CDC.
"Concern about the possibility that blood transfusion or organ donation may have transmitted West Nile infection to recipients of organs from a single donor has prompted the ongoing investigation that is now under way," Hughes said.
The kidneys, heart, and liver and of a Georgia woman, who died early last month in a car accident, were donated and implanted in the four patients.
At a news conference on Sunday, federal and state health authorities outlined the cases:
-- A patient in the Atlanta area who received an organ from the woman became ill August 15 with fever and encephalitis. The patient is recovering and being tested for the West Nile virus.
-- A second transplant patient in the Atlanta area came down with fever and encephalitis August 19 and died 10 days later. An autopsy showed evidence "consistent with West Nile or related virus infection."
-- A heart transplant patient in South Florida tested positive for the West Nile virus.
-- A transplant patient in the Jacksonville area came down with symptoms milder than the rest. Testing is under way on samples from that patient.
Tests are also being done on forensic samples from the organ donor, but even if they turn out positive for West Nile, authorities are unsure how the woman may have contracted the virus.
She received blood transfusions from 37 donors before she died, the CDC said, raising the possibility she contracted the virus through the transfusions.
Authorities were recalling all other blood products from those donors, though they couldn't rule out the possibility that some of them have already been used by other patients.
It is also possible that the organ donor was bitten by an infected mosquito before she entered the hospital, doctors said.
They said they have not ruled out the possibility that the transplant patients themselves were bitten by infected mosquitoes.
Even with the specter of infections through tainted blood, health authorities upheld the safety of the nation's blood supply.
The risks associated with transmission by blood are "very low," Hughes said.
There are currently no FDA-approved tests that could be used to screen blood products or organs for West Nile. Still, Hughes said, the risk is low enough that there is no need for a moratorium on blood transfusions.
Dr. Jesse Goodman, an official with the FDA, said that if the human-to-human transmission is confirmed, there will be a great incentive for researchers to come up with a test that could detect the virus in infected people who are not yet showing any symptoms.
"The simpler kinds of tests for antibodies won't work," Goodman said, because many asymptomatic patients do not produce a significant number of antibodies to fight the virus.
"That's been an area of a lot of research," Goodman said, noting that the result has been a number of "promising technologies."
The FDA said that even before the Georgia and Florida cases came to its attention, it was working with local health authorities to ensure that the risk of transmitting the virus through blood transfusions remained low.
"Two weeks ago we issued an alert to blood banks" to be sure adequate safety measures were in place, Goodman said.
If the human-to-human transmission is confirmed, it would be the first known case of its kind.
All previously documented cases of West Nile infection in people are believed to have come from mosquitoes. Public health officials emphasize that the virus cannot be transmitted through casual contact with an infected person.
The West Nile epidemic exploded this summer, three years after it was first detected in birds, horses and eventually humans in the northeastern United States.
At least 555 cases have been confirmed across 26 states and the District of Columbia, according to the CDC, and 28 deaths have been attributed to the disease.
More than a third of the infections have been in Louisiana, where eight people have died.
-- CNN Medical News Producer Miriam Falco contributed to this report.
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