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Mosquitoes harbor more than West Nile

The CDC says a specific type of mosquito, the culex, is most responsible for spreading the West Nile virus.  

By Thurston Hatcher

ATLANTA, Georgia (CNN) -- From the streets of Brooklyn to the Louisiana bayous, the recent West Nile virus scare has Americans scrambling for mosquito repellent.

But while the virus has killed several people in the United States since 1999, including a 71-year-old Atlanta woman earlier this month, experts say other mosquito-borne diseases in the United States pose as much danger, or even more.

Just last month, Eastern equine encephalitis took the life of a 9-year-old boy in the Florida Panhandle.

"By far, Eastern equine encephalitis is the more dangerous of the mosquito-borne diseases that really deserves the coverage," said Jonathan Day, a professor of medical entomology at the University of Florida's Institute of Food and Agricultural Sciences in Vero Beach.

Symptoms of Eastern equine encephalitis range from a mild flu-like illness to coma or death, and it can cause long-term neurological damage, including blurred vision and impaired mental ability. More than 150 cases have been confirmed in humans since 1964, according to the CDC. A vaccine is available for horses but not for humans.

"It is a really nasty disease and much more threatening if you get it," Day said.

Another threat comes from St. Louis encephalitis. Closely related to West Nile virus, it is diagnosed in about 130 Americans each year, according to the Centers for Disease Control and Prevention.

West Nile newer

Experts suggest the novelty of West Nile explains its notoriety.

"It moved so quickly and it's new, so we sort of look at it as more severe or more serious than those viruses, but in reality, in individual cases, that may not be the situation," said Dawn Wesson, associate professor of tropical medicine at the Tulane School of Public Health in New Orleans, Louisiana.

The first case of the West Nile virus in the Western Hemisphere was reported in the New York area in 1999. Since then, nine deaths have occurred in the New York and New Jersey metropolitan areas.

The fact that West Nile first surfaced in the nation's media capital may also have something to do with it, Day said.

"It has just had a media blitz since 1999, and it really hasn't stopped. You get a media report with every new dead bird, just about," he said.

The virus is cause for concern, not panic, Wesson said.

"Chances are if you get infected with West Nile you're not going to die from it and you're not going to become severely ill from it," Wesson said.

Global diseases

Malaria, although relatively rare in the United States, is one of the world's most devastating mosquito-borne diseases. It's actually caused by a parasite rather than a virus.

"In terms of mortality and morbidity of a specific mosquito-transmitted disease, malaria is by far the worst," Wesson said.

An estimated 300 million to 500 million cases of malaria occur each year, mainly in sub-Saharan Africa, and 1 million people die from it, according to the World Health Organization. The CDC says about 1,200 cases are diagnosed in the United States, typically in immigrants and travelers returning from overseas.

Another dangerous disease from mosquitoes is dengue fever, which the WHO says infects about 50 million people each year. The more severe dengue hemorrhagic fever is considered a leading cause of infant deaths in several Asian countries.

Yellow fever remains a public health threat in South America and parts of Africa, with about 200,000 cases each year and 30,000 deaths, according to WHO estimates.

Lymphatic filariasis, while not usually life-threatening, can damage the lymph system and kidneys. It can lead to swelling and elephantiasis, the hardening and thickening of the skin.

One virus that cannot be spread by mosquitoes is HIV, which causes AIDS.

Taking precautions

Even if most people aren't at risk for the West Nile virus or any other disease, Wesson says people should still make a habit of avoiding mosquitoes and keeping them from breeding.

Precautions include wearing repellent, particularly in the late afternoon and evening when mosquitoes are most prevalent, and eliminating standing water where they can breed.

"Even if you don't every single year have virally transmitted diseases, they do pop up occasionally," Wesson said. "A mosquito bite here and there infrequently is probably not much to worry about, but in terms of heavy exposure, you would probably want to protect yourself."

• Centers for Disease Control and Prevention
• World Health Organization
• Tulane School of Public Health and Tropical Medicine
• University of Florida Institute of Food and Agricultural Sciences

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