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Dengue Outbreak Hits Key West, Fla.

5% of Key West Population Infected in 2009; New Case Suggests Ongoing Outbreak
By
WebMD Health News
Reviewed by Laura J. Martin, MD

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May 20, 2010 - An "extended outbreak" of dengue fever is ongoing in Key West, Fla., where some 5% of residents were infected last fall.

The latest case of the mosquito-borne disease was in mid-April. It's not yet clear whether the April case is a continuation of the 2009 outbreak or a new outbreak from a different dengue strain.

Although only 28 cases have been definitively identified, blood tests conducted in September 2009 detected evidence of recent infection in 5.4% of 240 randomly selected residents.

"The best estimate from the survey is that about 5% of the population of Key West was infected in 2009 with dengue," dengue expert Christopher J. Gregory, MD, of the CDC's Epidemic Intelligence Service, tells WebMD.

"We had hoped we'd be able to eliminate the disease from Key West and took every effort to do so," Robert Eadie, administrator of the Monroe County Health Department, said in an April news release. "However, the [newly] confirmed case is not totally unexpected in that once dengue fever has been established in an area, it is truly almost impossible to completely eradicate it."

Once a rare disease, dengue has been spreading around the globe at an alarming rate. It's become entrenched -- endemic, as infectious disease experts say -- in Mexico and in the Caribbean, including Puerto Rico where Gregory is based.

The last U.S. "extended outbreak" was in Hawaii in 2001-2002. Except for small outbreaks along the Mexico border (linked to outbreaks in Mexican border cities), dengue has so far spared the continental U.S. That appears to be changing.

"The biggest thing people need to be aware of that it is possible to acquire dengue in the continental United States. That is widely underappreciated," Gregory says. "We have known for a while it is a possible risk, but this outbreak shows it is more than possible: It is something that did happen and could happen again."

In areas where dengue virus has become endemic, outbreaks tend to occur every six to eight months.

Despite the outbreak, neither the CDC nor the Florida Department of Health has issued travel warnings. Chris Tittel, spokesman for the Monroe County Health Department (which includes Key West), says health officials are simply stressing personal protection.

"We are just telling folks who come to visit that dengue is here, but not every mosquito carries dengue," Tittel tells WebMD. "We advise that people should not be overly concerned, but be aware and avoid mosquitoes."

The Monroe County Health Department has issued a health advisory urging residents to reduce mosquito-breeding areas, to repair windows and screens, to use air-conditioning, and to wear mosquito repellent.

Symptoms of Dengue Fever

Dengue fever ranges from asymptomatic infection (most common in school-age children) to, in rare cases, a fatal hemorrhagic disease. There is no vaccine and no specific treatment.

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