Dengue Fever, A Tropical Disease, Buzzes Back Into U.S. Seven decades after public health officials thought they'd eradicated dengue fever, the disease has once again become a scourge in Florida. More than 90 cases have been reported there since 2009. The stakes are high: The same mosquito that carries dengue is also a vector for yellow fever.
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Tropical Disease Buzzes Back Into U.S.

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Tropical Disease Buzzes Back Into U.S.

Tropical Disease Buzzes Back Into U.S.

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Tropical diseases like dengue fever sound like they belong in faraway places. But in the last several years, some have begun showing up in the continental U.S. In the second of our stories on the resurgence of dengue fever, NPR's Greg Allen reports public health officials in Key West are combating a scourge they thought they'd eradicated some 70 years ago.

GREG ALLEN: Until recently, a locally contracted case of dengue fever had not been seen in Florida since 1934. That suddenly changed in 2009, when doctors in Key West began seeing it in people who had not traveled outside of the area. There were 27 cases that year. Last year, 66 people in Key West contracted dengue. Arlo Haskell was one of them.

Mr. ARLO HASKELL: I had it really bad for three or four days, with a fever of about 103 and a pain in the joints and in the eyes.

ALLEN: Because of the joint pain, it's sometimes called break-bone fever.

Mark Whiteside, the medical director with the county health department, says while debilitating, dengue is rarely fatal.

Dr. MARK WHITESIDE (Medical Director, Monroe County Health Department): Typical dengue fever is a severe, flu-like illness. It might last a week or two. You might wish you were dead, but almost everybody gets over it.

ALLEN: Dengue is considered a serious public health threat here and in Hawaii, south Texas and other Florida counties where it's been reported. But compared to its resurgence in Latin America, the dengue outbreak in Key West is relatively minor.

The growth in global trade and international travel helped bring dengue to the U.S. But Dr. Whiteside says there's another important factor: the Aedes aegypti mosquito.

Dr. WHITESIDE: The carrier of dengue, the vector of dengue, Aedes aegypti, is more widespread and abundant than ever before in history. So, that's obviously part of the reason we have dengue back.

ALLEN: Last year, health officials in Key West conducted a campaign to educate the public about dengue and about what steps they should take to control mosquitoes around their homes: Dump standing water, use screens and air conditioning, wear mosquito repellent. So far, the results have not been encouraging. A survey conducted in January found that one out of five homes in the Keys provided breeding spots for Aedes aegypti.

(Soundbite of footsteps)

ALLEN: But here in Key West, controlling mosquitoes is serious business - too important to be left to volunteers or part-timers.

Mr. JOHN DAVID SNELL (Inspector, Mosquito Control District): You can see the gutter coming off the roof.

ALLEN: Right.

Mr. SNELL: And if you look in the water, you can actually see the larvae.

ALLEN: In the water, they're tiny, but clearly visible - quarter-inch-long larvae wriggling just under the surface.

John David Snell is an inspector with the local Mosquito Control District. He's one of 23 inspectors who spends every day going house to house throughout Key West looking for problem spots: unattended pools, open containers, anything that can capture rainwater and provide a place for mosquitoes to lay their eggs.

The remedies vary. In the backyard of a home in Key West's Old Town, Snell checks on a shallow pond that's been filled by rainwater. He opens a cooler that he's been carrying.

Mr. SNELL: In here, I have the mosquito-eating fish, the Gambusia.

ALLEN: Snell gently pours the fish - and the brackish water they're in - into the pond.

Mr. SNELL: In a pond this size, 20 fish will probably do the job. And, as long as the fish are happy in here, they'll reproduce, and the population of the fish will get bigger. And as long as there's water, we don't have to worry about mosquitoes in the pond.

ALLEN: The threat of dengue fever has made eliminating the Aedes aegypti a top priority for the Mosquito Control District. But that's easier said than done.

Dr. ANDREA LEAL (Entomologist, Deputy Director, Mosquito Control District): It's very difficult to even control this particular mosquito, because it does go inside of people's homes.

ALLEN: Andrea Leal, an entomologist who's the Mosquito Control District's deputy director, says Aedes aegypti mosquitoes thrive around people, and in some ways, Key West is an ideal environment.

Ms. LEAL: A lot of places here in Key West, they don't have screens. They leave doors wide open. So this particular mosquito, they can breed outside in, let's say, a water-holding bucket. And then once the adults come off, they'll move inside the home and feed on people inside the home.

ALLEN: So far this year, there have been no cases of dengue fever reported in Key West. But the rainy season - when mosquitoes peak - is just beginning.

One of the top experts on dengue fever, Duane Gubler of Duke University, recently visited Key West. He says the Aedes aegypti mosquito is also a disease vector for other tropical diseases that are beginning to show a resurgence, including yellow fever.

Mr. DUANE GUBLER (Duke University Professor): If we start seeing urban transmission of yellow fever in tropical America, it's going to move very quickly to the United States. So I think the risk of yellow fever is very real.

ALLEN: Gubler believes with enough work, it's possible not just to control the Aedes aegypti mosquito, but to eradicate it in Key West. After all, he points out, it's an island just four miles long and two miles wide.

Greg Allen, NPR News, Miami.

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