New Test For West Nile Virus
FDA Approves Rapid Detection Test for Mosquito-Bourne Infection
July 10, 2003 -- It's official; West Nile virus season is back. The CDC confirmed the first human case this week in South Carolina -- and just in time, the FDA has approved a new test that can help rapidly diagnose a person carrying the virus.
The new blood test works by detecting antibodies to the virus, which are detectable within the first few days of the onset of the infection.
Called the IgM Capture ELISA test, it is designed for use in patients with severe symptoms consistent with viral encephalitis/meningitis. The ease of the test makes it possible for all hospitals to test patients rather than needing to send blood samples to the CDC in Atlanta, Ga. for evaluation.
Health officials say the approval is timely. "This test provides a useful tool to combat the important public health problem of West Nile virus infection, just in time for the start of the West Nile season," says FDA Commissioner Mark B. McClellan, MD, PhD. Peak West Nile season usually begins in July and ends in October.
The FDA based their approval on 1,000 patient samples. The test correctly identified antibodies to the virus in 90 to 99% of West Nile cases. FDA officials say while the test is a valuable aid in the diagnosis of the West Nile virus, they recommend doctors use additional testing for confirmation of the infection because of the similarities between other viruses in the same family.
Most patients infected with the virus have mild, flu-like symptoms or none at all. But in those with weakened immune systems or the elderly it can be lethal, sometimes causing encephalitis, an inflammation of the brain.
The virus first appeared in the U.S. in 1999 but is now in virtually all parts of the country and parts of Canada. Birds carry the virus but it is spread to humans by mosquitoes that have also bitten infected birds.
SOURCE: News Release, FDA.