West Nile screening necessary for blood, says FDA

ATLANTA -- Government health officials Thursday said West Nile can apparently spread by transfusion, and they announced that all blood donations will probably be screened for the virus as soon as a test can be developed.

"Since this transmission by transfusion appears likely, it is likely also that we will need to move toward testing of donor blood," said Dr. Jesse Goodman of the Food and Drug Administration. "While the investigation is ongoing, we believe there's sufficient evidence when you put it all together that there likely is a risk."

Goodman said he could not predict how long it would take to develop such a test or how much it would cost.

"What we're trying to do here is jump-start this process ... so we can get a test as soon as possible," he said.

Goodman spoke after the Centers for Disease Control and Prevention released information that suggests that the virus can survive in donated blood for several days and that some blood recipients may have been sickened by infected blood.

A woman in Mississippi caught West Nile after receiving transfusions from three infected donors. CDC doctors called that case "highly suspicious" and said that West Nile "probably can be spread by transfusion."

Previously, doctors were not sure whether it was possible to spread West Nile through blood, although a Georgia case in which donated organs spread the virus to four recipients in August raised that possibility.

Blood banks said they expected the FDA's announcement.

Dr. Louis Katz, president-elect of industry group America's Blood Centers, said the important question is not whether West Nile can be transmitted through blood, because it probably can, but whether it is a threat big enough to warrant testing all donations.

"Does it rise to the level of appropriate screening? That's what we have to figure out," Katz said, adding that some diseases known to be spread through transfusion are not screened because they are so rare.

West Nile emerged in the United States just three years ago. The CDC has reported more than 1,700 human cases of West Nile virus so far this year, including 84 deaths.

The weak and elderly are especially vulnerable to the virus, which can cause encephalitis, a potentially lethal inflammation of the brain.

The CDC also warned doctors Thursday that West Nile can cause acute polio-like paralysis in some cases. Doctors were urged to test patients for West Nile if they report sudden, painless paralysis but do not appear to have had a stroke.

Most people who become infected with the virus suffer no ill effects at all; others develop only flu-like symptoms.

Researchers also point out that not all patients who receive tainted blood will become infected with West Nile. The CDC reported a July case in which a 55-year-old woman received contaminated blood after an orthopedic procedure but never tested positive for the virus.

While repeating that the benefits of blood transfusions far outweigh the risks of catching West Nile, Goodman said patients seeking elective surgery may want to talk with their doctors about delaying the procedure or donating their own blood to be used later on themselves.

The screening process could prove tricky because West Nile is not like other diseases screened out of the blood supply. For one thing, West Nile is much harder to detect than a virus such as HIV because there are relatively small amounts of West Nile virus in tainted blood.

Another complication is that because West Nile usually spends several days in the blood before symptoms show up, infected people may not immediately produce antibodies to fight West Nile. That means a screening test would have to search not for the antibodies but for the virus itself, a much more difficult task.