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CDC: New Mosquito Repellents Fight West Nile

Officials Hope More Options for Repellents Will Reduce Infection With West Nile Virus
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WebMD Health News

April 28, 2005 - The CDC says it is adding two new forms of mosquito repellentmosquito repellent to its list of recommended products in the hopes of encouraging more Americans to guard against West Nile virus this spring and summer.

The agency says repellents containing picaridin and oil of lemon eucalyptus can both be considered along with DEET,DEET, the active ingredient in most bug sprays on U.S. shelves. Officials say DEET remains highly safe and effective but that more consumer choices could help encourage use of repellents.

The primary way that people become infected with West Nile virus is through the bite of an infected mosquito. The infected mosquitoes picked up the virus after biting infected birds.

Picaridin, also known as KBR 3023, has been on sale for years in Asia, Australia, and Europe. It was only recently approved for use in mosquito sprays by the Environmental Protection Agency. The chemical has already hit stores in at least one product, Cutter Advanced repellent. Oil of lemon eucalyptus, also called p-menthane 3,8-diol, or PMD, is available in a number of sprays and lotions.

Studies show that picaridin works as well as similar concentrations of DEET, while oil of lemon eucalyptus repels insectsoil of lemon eucalyptus repels insects about as well as low concentrations of DEET. Because picaridin is only available in a 7% formulation, neither product will prevent mosquito bites for as long as high-concentration DEET will, CDC officials say.

"The key is that people remember to use a repellent in the first place ... no matter which of these repellents they are using," says Emily Zielinski-Gutierrez, PhD, a behavioral scientist in CDC's vector-borne infectious diseases division.

According to the CDC, mosquito repellents containing oil of lemon eucalyptus should not be used on children under the age of 3 years. "The best thing a consumer can do is look at the label because the label will give the approved usage," Zielinski-Gutierrez says.

Only about 40% of Americans use insect repellent on a regular basis, and the percentages are only about half that in Western states like California, Oregon, and Washington, she says.

But officials are hoping to dampen the impact of West Nile, which has already infected about 1 million Americans since its debut on the East Coast in the late 1990s. The disease is now found in all of the lower 48 states except Washington.

"It would not surprise me to find it in Washington state this year," says Lyle Petersen, MD, director of the CDC Division of Vector-Borne Infectious Diseases. "It's virtually on Washington state's border at this point."

The CDC recommends that people use mosquito repellent any time they go outside, especially during dawn-to-dusk hours when the insects are most active. Repellent should be reapplied as soon as mosquitoes begin biting again, the agency recommends.

The CDC recorded 2,470 West Nile cases last year, including 88 deaths. Peterson warns that the actual number of cases is much higher since only a fraction is ever reported to authorities. People over 50 are most at risk for serious consequences and comprise the vast majority of fatal cases.

Most infections result in mild symptoms including fever. Severe consequences like encephalitis (inflammation of the brain and its surrounding membrane) and paralysis arise in about one in 150 cases. Rates of serious disease are up to 40 times higher in people with compromised immune systems because of organ transplants.

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