WASHINGTON, Sept. 24 (UPI) -- West Nile virus infections appear to be declining as mosquito populations drop off with the onset of colder weather, but the virus will return next summer and in the meantime the federal government is scrambling to develop a vaccine and tests to detect it in the blood supply, health officials said Tuesday.
Because officials now think the virus can be transmitted via blood transfusions, the Food and Drug Administration is working with blood banks and medical diagnostics manufacturers to develop a test for screening blood. Jesse Goodman, deputy director of FDA's Center for Biologics, Evaluation and Research, said at a Senate hearing the agency expects the test to be ready by next year in time for the mosquito season.
The FDA also is working on new techniques for inactivating pathogens in the blood supply, Goodman said, although he did not elaborate on these techniques or when they might be available.
The National Institutes of Health is developing a vaccine against West Nile virus and could have one ready in as little as three years, Anthony Fauci, director of the NIH's National Institute of Allergy and Infectious Diseases, told senators.
This summer saw the worst outbreak of the virus since it first hit the United States in 1999. Fortunately, human cases of West Nile virus infection have peaked this year and appear to be on the decline, said Julie Gerberding, director of the Centers for Disease Control and Prevention in Atlanta.
The CDC reported as of Tuesday the number of West Nile cases topped the 2,000 mark, confirming 98 deaths in 2,072 cases. Illinois, the state reporting the most cases and deaths, upped its death toll to 29 in 518 cases after the CDC figures were released. Indiana reported its third probable West Nile death and Virginia reported its first -- all of which have yet to be counted by the CDC.
Fauci said cases of the virus could decline next year if mosquito control programs are effective and people adhere to personal precautions such as wearing insect repellent. But if cases do not decline or the virus returns in subsequent years, then it would be prudent to have a vaccine to protect those most at risk.
So far the highest-risk group seems to consist of people over 50 and the immunocompromised, including cancer patients and people with AIDS.
"We would anticipate expansion next year further into the West coast," Gerberding said, noting it is too soon to tell where the virus is heading for certain but it is possible to predict where the next human case will occur by monitoring birds and other animals, which act as reservoirs for the disease and transmit it to mosquitoes.
The disease is here to stay, Gerberding said, adding, "It is just about impossible to completely eliminate it" because it is so embedded in the bird and mosquito populations.
The CDC also is concerned the virus could spread to the Caribbean -- one human case already has been detected there -- as well as Central and South America.
State health officials testified they are concerned the virus could return with a vengeance next summer and urged Congress to authorize more funding to the states for mosquito control and monitoring of infected birds.
"I think (Arkansas) is going to have a very bad year next year," said Fay Boozman, director of the Arkansas Department of Health. Arkansas has had nine cases so far this year, but Boozman said he predicts the state will see a dramatic increase next year because infected bird and mosquito populations may survive the winter.
A major concern for next year is people who never develop any symptoms may unwittingly donate blood and infect the blood supply, FDA's Goodman said. Blood banks bar people from donating if they have a fever or achiness -- symptoms that suggest a West Nile infection -- but most people never develop any symptoms and thus would still be allowed to donate. "So that's why we need a screening test," Goodman said.
The test probably would incorporate technology called polymerase chain reaction, which has been used to develop blood screening tests for other viruses, including HIV and hepatitis C, he said. Goodman noted the agency also is concerned about the risk of spreading the disease from organ and tissue transplants and wants to develop screening tests for these as well.
John Lumpkin, director of the Illinois department of public health, said people might be able to contract the virus from contact with blood from a recently killed animal. He cautioned hunters to wear gloves to protect themselves when gutting and cleaning their catch.
Fauci said research has found that animals infected with Yellow fever or Dengue fever appear to receive some protection from West Nile. That finding should prove useful for constructing a vaccine and has allowed researchers to speed up development by several years, he said.
The vaccine being developed takes genes from West Nile and inserts them into the Yellow fever vaccine. The agency soon will begin testing it in humans, Fauci said. The agency also is studying people who have been vaccinated against Yellow fever to determine if they are less likely to develop serious illness due to West Nile.
The NIH will use the winter months to investigate certain mysteries surrounding the disease, such as its newly detected ability to cause polio-like paralysis symptoms, Fauci said. "It's new and alarming," he said, adding the virus did not cause that kind of problem in Europe and the Middle East, where it existed for several years before making its way to the U.S.
Officials stressed simple precautions, such as draining standing water and wearing insect repellent, could help many people avoid the disease. State officials will implement mosquito control programs next year but even the best efforts will only reduce mosquito populations by half, Lumpkin said.
(With additional reporting by Marcy Kreiter, UPI Chicago Bureau)