FDA Consumer magazine
September-October 2003 Issue

First Test Approved to Help Detect West Nile Virus

By Carol Rados

The Food and Drug Administration has cleared the first test that will help physicians diagnose cases of potentially deadly West Nile virus earlier than with current methods.

The West Nile Virus IgM Capture ELISA test is intended to be used in people who have symptoms of viral encephalitis or meningitis, which are serious inflammatory conditions of the brain or spinal cord that may occur in people infected with the virus.

"The rapid review and approval of this blood test, which uses antibody levels to identify persons who were recently exposed to West Nile virus, reflects FDA's commitment to making safe and effective medical products available promptly," says FDA Commissioner Mark B. McClellan, M.D., Ph.D. The new test works by detecting the levels of IgM, a particular type of antibody to West Nile virus, in blood serum. It is manufactured by PanBio Ltd. of Windsor, Australia.

West Nile virus is a mosquito-borne virus first detected in the United States in 1999. While it often causes a mild infection that clears without further treatment, some people, especially those over 50, develop severe infections resulting in neurological disease and even death. The virus is most prevalent during peak mosquito season, beginning in July and ending in October.

By 2002, West Nile virus had spread to most of the continental United States. The CDC reported this season's first human case of West Nile virus in the United States in early July. As of early August, three deaths in Texas and Alabama had been attributed to the virus. The CDC says that West Nile virus activity detected in humans began a "significant uptick" in early August 2003.

The new diagnostic test is a significant breakthrough in the detection of West Nile virus. However, it's important to know that it is not a donor screening test, but is one of several tools used by the physician to determine if the patient is infected. Results from the IgM Capture ELISA must be confirmed with other laboratory tests as part of a comprehensive evaluation. The test is designed to be used in cases when someone has symptoms of West Nile encephalitis or meningitis--headache, high fever, neck stiffness, stupor, disorientation, coma, tremors, convulsions, muscle weakness, and paralysis.

In addition to its usefulness for diagnosing individuals with the infection, the test has the potential to help monitor the scope and spread of the disease.

The FDA has established guidance and procedures to avoid collection and use of blood that might be at risk for transmitting West Nile virus. The agency is cooperating with the country's blood organizations, both in the laboratory and in epidemiological investigations of the virus. In August 2002, prior to any actual report of transmission, the FDA alerted the blood industry to be vigilant in excluding symptomatic donors and then later that year provided guidance to blood establishments on procedures to protect the blood supply. The FDA updated this guidance in May 2003, based on experience with the 2002 outbreak.

Additionally, the agency is working with manufacturers to expedite development of necessary medical products, such as screening tests and additional diagnostic methods. Experimental donor screening tests have been put into place and have been available nationwide since July 1, 2003. These tests add a measure of safety and will prevent contaminated blood from entering the nation's blood supply.

Other federal efforts are ongoing to combat West Nile virus. The National Institutes of Health (NIH) is supporting ongoing research at universities and companies nationwide aimed at developing the public health tools to help fight the infection. Currently the NIH is funding four areas of research for West Nile virus: diagnosis, prevention, therapy, and basic research that looks at the virus as it replicates in animals, humans, and mosquitoes. In the area of prevention, the NIH is supporting three different approaches to vaccines, including a live vaccine made by mixing West Nile virus with the already established yellow fever vaccine. Through its grants and contracts, the NIH is the largest supporter of infectious disease research in the United States.

For now, the CDC, the FDA and the NIH all agree that the most important message about the virus is that people need to be prepared and take the steps necessary to prevent mosquito bites and avoid exposure, especially until treatment or vaccines are available to add additional layers of protection.

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For More Information

See "West Nile Virus: Reducing the Risk" in the January–February 2003 issue of FDA Consumer.

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Reduce the Risk of West Nile Virus

1. Avoid mosquito bites

Cover up. Wear long-sleeved shirts, long pants and socks sprayed with repellent while outdoors.
Avoid mosquitoes, which often bite between dusk and dawn.
Limit time outdoors during these hours.
Spray insect repellent containing DEET (look for N, N-diethyl-m-toluamide) on exposed skin outdoors.
Spray clothing with repellents containing DEET or permethrin.
Don't spray repellent on skin under clothing.
Don't use permethrin on skin.
Use repellent carefully.
Don't put repellent on kids' hands because it may get into their mouths or eyes.

2. Mosquito-proof your home

Install or fix window and door screens.
Drain standing water, where mosquitoes like to breed.
Look around every week for possible mosquito breeding places.
Empty water from buckets, cans, pool covers, flowerpots, and other items.
Throw away or cover up stored tires and other items not being used.
Clean outdoor pet water bowls weekly.
Check to see if rain gutters are clogged.

3. Help your community

Dead birds help health departments track West Nile virus.
Check with your local or state health department to find out their policy for reporting dead birds.

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