The following summary is compiled from the transcript and news reports from the September 24, 2002 joint hearing of two subcommittees of the Senate Committee on Health, Education, Labor and Pensions and the Governmental Affairs Committee about West Nile Virus.
Witnesses:
Summary:
Witnesses indicated that while West Nile virus (WNV) has been established firmly in the mosquito and bird populations, they expect that WNV cases will drop sharply as more people gain immunity and communities quickly eradicate mosquito breeding grounds. As children and young adults become immune today, they will face reduced risks to WNV when they are older since the most vulnerable segments of the population are the elderly and the immune-deficient.
There are expectations that if WNV behaves like the other flaviviruses, such as St. Louis encephalitis virus, there will be cycles of little infection punctuated with outbreaks. One proposed theory is that most birds gain immunity from the previous year and hence the viral reservoir is exhausted for the following years. Therefore, John Lumpkin, Director of Illinois Dept of Public Health, speculated that noticing falling immunity levels in bird flocks may provide us with warnings of the reemergence of WNV.
Since CDC believes that WNV can be transmitted through blood transfusions and organ donations, there is need to develop a blood test to screen blood banks. Most people who become infected never develop symptoms and may donate blood without knowing.
Jesse Goodman, Deputy Director of FDA's Center for Biologics, Evaluation and Research said that by next summer they hope to have adapted nucleic acid testing (NAT) that detects low levels of other viruses to test for WNV. Goodman said that though the risk to the blood supply was low since WNV only stays in the blood stream for a short time, there may be sufficient risk to warrant widespread use of this test voluntarily or experimentally. It may take years to fully evaluate an adequate method of screening WNV, but an experimental test may be employed as was done when the 1980s AIDS blood test was being developed.
Jay Epstein, Director of blood research and review at the FDA, said that though an unlicensed test cannot be required, he expects that most blood centers would choose to use this test. Goodman also said that they are working on finding new techniques to inactivate pathogens in the blood.
John Lumpkin, Director of Illinois Department of Public Health, has also warned that people may be able to contract WNV from the blood of recently killed animals. Hunters are recommended to wear gloves when cutting and cleaning their game.
Anthony Fauci, head of the National Institute of Allergy and Infectious Diseases at the NIH, said that research for a WNV vaccine based on the existing yellow fever vaccine may be ready in three years. WNV genes have been spliced into the yellow fever vaccine to create a hybrid vaccine that has proven effective in animal studies. Acambis, a biotechnology company, is planning to conduct human testing in 2003. The NIH will also be testing for cross-protection in people vaccinated against yellow fever (e.g., travellers to parts of Africa and South America) since there seems to be a link between immunity to yellow fever, dengue fever and St Louis encephalitis and immunity to WNV.
Sources:
Hearing called jointly by the Senate Committee on Health, Education, Labor and Pensions and the Governmental Affairs Committee. Washington DC. September 24, 2002. Transcript: http://www.cfe.cornell.edu/erap/WNV/WNVEducDocs/SenateHearing9-24-02.html
US Scrambles to Control West Nile Virus. NewsMax.com. Sept 25, 2002. http://www.newsmax.com/archives/articles/2002/9/24/175547.shtml
Scientists predict vaccine against West Nile Virus within three years. USA Today. Sept 25, 2002. http://www.usatoday.com/news/health/2002-09-25-vaccine-west-nile_x.htm