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Routine testing for the presence of West Nile virus in donated blood may be in place by next summer, an official of the Food and Drug Administration told a Senate committee yesterday.
It will take several years to fully evaluate and license a method for West Nile screening of blood, Jesse L. Goodman, deputy director of the FDA's Center for Biologics Evaluation and Research, told the legislators. However, the current risk to the blood supply from West Nile virus is big enough that the agency might permit widespread use of the test on a voluntary or experimental basis during that period. Such an arrangement was permitted in the 1980s when the AIDS blood test was being developed.
Goodman said several companies are working on a West Nile test, which is likely to be a version of the one now used in research laboratories to detect viral genes in minute concentrations.
"What we are hearing from the companies and blood organizations is that they are hopeful this will be able to be done in time for the next transmission season," he said at a hearing called jointly by the Senate Committee on Health, Education, Labor and Pensions and the Governmental Affairs Committee. "I think an optimistic scenario would be to have this available for next summer, at least."
Investigators at the Centers for Disease Control and Prevention (CDC) are now convinced the virus can be contracted through infected blood or organs.
The FDA couldn't require blood centers to use a test that was unlicensed and under investigation, Jay S. Epstein, director of blood research and review at the FDA, said after the hearing. He said, however, that he thinks most would choose to do so, and that the agency would allow it.
There have been about 2,000 cases and at least 98 deaths from the virus this year in the United States. Thirty-two states, and the District, have reported human infections.
The microbe is transmitted by mosquito bites. It is spread mainly from infected birds, although the virus infects other animal species, such as horses. Data from previous outbreaks suggest that in high-prevalence areas, about 1 in 200 mosquitoes carries the virus.
Illinois has been hardest hit, with 518 cases and 29 deaths to date. Most were in the Chicago area.
The reason for the high prevalence there is unknown. However, Illinois had a nearly identical experience in 1975 when the United States experienced one of the periodic outbreaks of St. Louis encephalitis virus. That microbe, which is closely related to West Nile, is also transmitted by mosquitoes. Of the roughly 2,000 cases recorded nationwide, Illinois had 578, with 47 deaths.
Julie Louise Gerberding, the CDC's new director, testified that West Nile virus has been found in Canada, and there is evidence of its presence in Mexico. "We would anticipate further extension next year into the West Coast," Gerberding said.
Anthony S. Fauci, head of the National Institute of Allergy and Infectious Diseases at the National Institutes of Health, said research is underway on a vaccine made from the existing yellow fever vaccine with West Nile genes spliced in. If that hybrid vaccine works -- tests in people are scheduled for 2003 -- a West Nile vaccine might be available in about three years.
If West Nile turns out to behave like St. Louis encephalitis virus, there are likely to be sporadic outbreaks interspersed in long periods in which there is little evidence of the disease.
John R. Lumpkin, director of the Illinois Department of Public Health, said he hopes West Nile researchers will look closer at the role played by birds in the virus's transmission cycle.
In 1976, the year after the severe St. Louis encephalitis virus outbreak, Illinois had only 19 cases of that disease. One theory for the steep decline was that most birds were immune from previous infection and that the viral reservoir in them was largely dried up.
Lumpkin speculated that declining West Nile immunity in bird flocks might function as an early warning that the virus might soon emerge and circulate again.
"We didn't do that in 1975," he said, referring to basic research on West Nile transmission. "Maybe if we had, we'd be better prepared for West Nile now."
[ Washingtonpost.com ]
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Last Revised at December 10, 2007 by Lusine Kazoyan, M.D.
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