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TUESDAY, July 15, 2003 (HealthDayNews) -- There have been four human cases of West Nile virus in the United States this year, and 32 states have reported the virus' presence in mosquitoes, birds, animals or humans.
While the human tally is on par with last year's count, many more states are reporting West Nile activity than in 2002, federal health officials said Tuesday.
"This is exactly the same number of human cases as we had a year ago. What's a little concerning is that many more states are recording West Nile activity this year compared to last year," Dr. Julie Gerberding, director of the U.S. Centers for Disease Control and Prevention, said at a press conference.
"We had just over 20 states last year, so the overall national activity level is increased. We anticipate an upswing toward the end of July and August so we have to stay tuned to fully appreciate the full scope and magnitude," she added.
West Nile virus is spread by mosquitoes that pick it up when feeding on infected birds and animals. About one in 200 humans infected with the virus actually become seriously ill with encephalitis (inflammation of the brain) or meningitis (inflammation of the lining of the brain and spinal cord). About 20 in 200 will experience less severe, flu-like symptoms, including fever, headache, muscle aches and fatigue.
Three of this year's human cases are in Texas and one in South Carolina, areas that have had high levels of virus activity in the past. A fifth case is under investigation in a third, as yet unnamed, state, Gerberding said.
The virus' presence in mosquitoes, birds and animals seems to be concentrated in the Midwest so far, though that's likely to change, health officials said.
"It's very early to predict what we're going to see on the West Coast," Gerberding said. "The surveillance system is very active in the western states right now. We won't be at all surprised if it does emerge there."
The virus made its first North American appearance in New York City in 1999 and has been proceeding west ever since.
One blood donor in Harris County, Texas, was found to be infected after undergoing one of the newly available commercial tests for the virus. The person had no symptoms, however, so this was not included in the case count, officials said.
The person was detected by one of the new screening tests released under a U.S. Food and Drug Administration (FDA) Investigational New Drug protocol.
"This demonstrated that the test worked," said Dr. Jay Epstein, director of the FDA's Office of Blood Research and Review. "There are a small number of additional suspect positives that are being further investigated and because we now have a human epidemic, we do expect to see more pickups among donors."
The development and implementation of two commercial tests to screen the blood supply was just one advance made in the past year. Those tests were put in place in high-risk areas starting in mid-June and have been available nationwide since July 1, officials said.
"We can never say that there's no risk, but remarkably speedy advances in testing and test development have put us in much better shape this year than last year," Gerberding said. "It's clearly an improvement and a big step forward."
Meanwhile, research is proceeding at the National Institutes of Health (NIH) into antiviral medications, vaccines and basic research.
Perhaps the most promising vaccine research thus far involves a chimeric virus that combines the proven vaccine for yellow fever with proteins from the West Nile virus.
"This has been taken all the way through testing in primates," said Dr. James Meegan, virology program officer at National Institute of Allergy and Infectious Diseases, part of the NIH. "Pre-clinical tests have shown it to be safe and efficacious. The company is now applying to test that vaccine in humans, probably by the end of the summer if everything goes all right. Right now, this looks like our best bet."
Research is also under way into the development of an inactive protein virus and a DNA vaccine, both of which have a long way to go before they can be tested in humans, officials said.
About 600 compounds have been tested in petri dishes to see if they inhibit replication of the West Nile virus. So far, 20 to 30 show some promise and are being prepared for animal testing, Meegan said. Scientists are also investigating the potential of using antibodies from people who have recovered from West Nile virus to treat current patients.
While research is important, wearing long sleeves and long pants may be your best protection this season.
"For right now, the most important message is to be prepared," Gerberding said.
That means keeping your skin covered, especially during peak mosquito hours (evenings and early mornings), and wearing insect repellant (preferably one containing DEET). Also, keep screen doors and windows in good repair and, perhaps most important, get rid of standing pools of water in flower pots, tires and other receptacles that form mosquito breeding grounds.
More information
For more on West Nile virus, visit the U.S. Centers for Disease Control and Prevention. For more on the safety of the blood supply, try the American Association of Blood Banks.
