Dengue fever outbreak feared in Key West [Updated]

Federal officials said Tuesday that they fear an outbreak of dengue fever in Florida after a survey of Key West residents found that at least 5% had been infected or exposed to the virus. With the exception of a handful of isolated cases along the Texas-Mexico border, there had previously been no cases in the continental United States since 1946 and no outbreak in Florida since 1934.

[FOR THE RECORD: 1:56 p.m.: An earlier version of this post didn’t specify the “continental United States.”]

Dengue fever, which is characterized by a fever of 104 to 105 degrees, a widespread rash, headache, fatigue and muscle aches, is the most common disease caused by mosquito-transmitted viruses in the world. Each year, there are an estimated 500,000 to 1 million cases and about 25,000 deaths worldwide.

“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,” Dr. Harold Margolis, chief of the dengue branch at the Centers for Disease Control and Prevention, said in a statement.

Last September, a physician in New York notified the Monroe County (Fla.) Health Department about a suspected dengue fever case in a New York resident whose only travel had been to Key West. In the next two weeks, two dengue infections in Key West residents who had not traveled elsewhere were identified. By the end of the year, 27 cases had been identified.

Researchers from CDC and the Florida health department reported in Atlanta at an International Conference on Emerging Infectious Diseases that they then collected 240 blood samples from randomly selected households in Key West. About 5% of them showed the dengue virus itself or antibodies against it, indicating that about 1,000 residents of the city have been infected or exposed to the virus.

“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.