WEDNESDAY, July 14 (HealthDay News) -- Health officials monitoring residents of Key West, Fla., for exposure to dengue virus were alarmed to find that more than 5 percent of the population (about 1,000 people) were exposed to the pathogen in 2009.
"We're concerned that if dengue gains a foothold in Key West, it will travel to other southern cities where the mosquito that transmits dengue is present, like Miami," Harold Margolis, chief of the dengue branch at the U.S. Centers for Disease Control and Prevention, said in a CDC news release.
Dengue -- the most common virus transmitted by mosquitoes -- causes up to 100 million infections and 25,000 deaths worldwide each year. Between 1946 and 1980, there were no reported cases of dengue acquired in the continental United States, and there hasn't been an outbreak in Florida since 1934, the CDC said.
Dengue fever typically involves a high fever, headache, rash and pain in the muscles, bones and joints. Infection can, in rare cases, infection can lead to a more severe illness called dengue hemorrhagic fever, which can prove fatal. There is no vaccine against dengue viruses.
"These cases [in Key West] represent the re-emergence of dengue fever in Florida and elsewhere in the United States after 75 years. These people had not traveled outside of Florida, so we need to determine if these cases are an isolated occurrence or if dengue has once again become endemic in the continental United States," Margolis said.
Since 1980, there have been a few locally acquired dengue cases in Texas along the Mexican border. These cases coincided with large outbreaks in neighboring Mexican cities, the authors of the news release noted.
Health officials started looking for dengue in Key West after a New York state resident developed a dengue infection after visiting Key West. By the end of 2009, 27 cases of dengue infection had been confirmed in Key West residents. As of the end of June 2010, an additional 12 cases of locally acquired dengue had been reported in Key West and surrounding areas.
Blood samples collected in 2009 from 240 people in randomly selected households in Key West found that 5 percent had dengue active in their systems or had dengue antibodies, suggesting that they'd experienced dengue disease within the previous three months.
As a result, officials at the CDC and the Florida Department of Health have continued monitoring for dengue cases in the Key West area.
"The mosquito that transmits dengue likes to bite in and around houses, during the day and at night when the lights are on," Margolis said. "To protect you and your family, CDC recommends using repellant on your skin while indoors or out. And when possible, wear long sleeves and pants for additional protection."
The U.S. National Institute of Allergy and Infectious Diseases has more about dengue fever.
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