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Full-Scale Assault Now Under Way as Key West District Battles Dengue

Swarms of them come from near and far, creating a furor in Key West, Florida.

“They” are not mosquitoes. They are representatives of the national and international news media, who journey to the southernmost tip of the continental United States to cover a story about the first dengue fever outbreak in Florida since the 1930s.

The dengue outbreak has captured the attention of traditional journalists and a host of bloggers. A Google search of “Dengue fever Key West” produced 793,000 results.

Employees of the Florida Keys Mosquito Control District have been pictured in The New York Times and followed by producers and photographers from CNN, Fox News and reporters from many other news outlets.

But behind the scenes, District Superintendent Mike Spoto and Deputy Director Andrea Leal are mounting a multipronged assault on Aedes aegypti and the habitat where the vector thrives.

Small City, Many Visitors

Key West is a major Florida tourist destination, with hundreds of thousands of visitors each year, and is a popular port of call for cruise ships from all over South America. But the 12-square-mile city itself has only about 11,000 households and a population of less than 26,000. The dengue outbreak has been centered in the Old Town section of the city, which makes up about half the total land area.

“The people of Key West are pretty laid back,” Spoto explained. “Many homes don’t have screens, and people often leave their houses wide open, so they are very much at risk of being bitten by infected mosquitoes.” Complicating the situation is the “enormous amount of fresh water” found in the many open wells and cisterns in the area, Spoto said.

Integrated Approach

To fight the dengue outbreak, the Florida Keys district is employing every appropriate tool in its arsenal in an integrated approach to combat the vector mosquitoes.

Along with a major investment in surveillance and public education, a key element of the district’s Ae. aegypti program is its domestic inspection effort. With a staff of 88 and as many as 35 part-time employees, the district’s inspectors go door-to-door to identify waterholding containers where the mosquitoes breed. Those include everything from refuse piles to the region’s ubiquitous bromeliad plants.

“Most people have been very cooperative about allowing us access to their properties,” Spoto added. “A few have balked, but since we have a public health advisory in place, we’ve been able to gain access even in cases where the residents have been reluctant.”

During their residential calls, district staff empty as much water as they can and then use backpack sprayers to treat other larval sources. Swamps, mangroves and low-lying areas near the city also are treated with larvicides.

Also to combat the Ae. aegypti mosquitoes, more than 5,300 lethal ovitraps have been employed around the city. And, with four helicopters and two fixed-wing aircraft, the Florida Keys district conducts significant adulticiding operations as surveillance indicates a need.

Spoto and Leal also said they are adjusting the product mix when necessary to avoid development of resistance and are experimenting with new approaches.

“This is a year-round effort for us because of our subtropical climate, so we are constantly seeking ways to improve our program in the interests of public health,” Spoto said.

Dengue Fever: World’s Most Common Vector-Borne Viral Disease

Dengue is the most common vector-borne viral disease in the world, causing an estimated 50–100 million infections and 25,000 deaths each year, according to the U.S. Centers for Disease Control and Prevention (CDC).

During 1946–1980, no cases of dengue acquired in the continental United States were reported. Since 1980, a few locally acquired U.S. cases have been confirmed along the Texas-Mexico border, temporally associated with large outbreaks in neighboring Mexican cities.

On September 1, 2009, a New York physician notified the Monroe County, Florida, Health Department and the Florida Department of Health of a suspected dengue case in a New York state resident whose only recent travel was to Key West, Florida.

CDC confirmed the diagnosis, and a press release was issued to notify the public and Key West physicians of the potential risk for locally acquired dengue infections. In the next two weeks, two dengue infections in Key West residents without recent travel were reported and confirmed.

By mid-August 2010, more than 50 cases of dengue had been confirmed during the last two years.