Five percent of Key West residents show evidence that they have been exposed to the virus that causes dengue fever, a mosquito-borne, potentially serious illness that had once disappeared from the United States, health officials said Tuesday.
The federal Centers for Disease Control and Prevention and the Florida Health Department tested a random sample of the island's 25,000 residents, examining antibodies in their blood, after three dengue cases surfaced in Key West last August, the first locally acquired cases reported in the state in four decades.
Officials said the sample taken last September showed that about 1,000 residents likely had been exposed to the tropical disease. The CDC says to date, 39 residents and visitors have gotten sick. Only one of those became seriously ill, Monroe County officials said.
Dengue fever is a flulike illness spread by the bite of an infected Aedes aegypti mosquito (ay-EE-deez ee-JIP-ty), a common urban mosquito in the U.S. and Caribbean. It is also known as breakbone fever because of the intense joint pain suffered in extreme cases.
"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 CDC's dengue branch, said in a statement.
He said dengue mosquitoes like to bite in and around homes, during the day and at night when the lights are on. He said Keys residents and visitors should use mosquito repellent both outside and indoors and, when possible, wear long sleeves and pants.
Key West officials say mosquito eradication efforts have been intensified and businesses and residents have been urged to keep outdoor flower pot trays and other containers free from standing freshwater, where the mosquitoes breed.
"Everything to eradicate the disease is being done," said Bob Eadie, administrator of the Monroe County Health Department.
According to the CDC, dengue infects an estimated 50 million to 100 million people worldwide each year and causes 25,000 deaths, a fatality rate that's a fraction of 1 percent. From 1946 to 1980, no cases of dengue acquired in the continental United States were reported, and there had not been a large outbreak in Florida since 1934.
Since 1980, some cases have been reported in Texas along the Mexican border, coinciding with large outbreaks in neighboring Mexican cities, the CDC said. Cases have also been reported in Puerto Rico.
Symptoms include a high fever and at least two of the following: severe headache; severe eye pain; joint, muscle or bone pain; rash; mild bleeding in the nose or gums or easy bruising; and low white blood cell count. There is no specific medication for dengue.
The CDC says people who think they have dengue should consult a doctor, use pain relievers with acetaminophen and avoid those containing ibuprofen, naproxen or aspirin. They should rest, drink plenty of fluids and avoid mosquito bites to prevent spread of the disease. Generally, young children and those with their first dengue infection have a milder illness than older children and adults, the CDC says.
Severe symptoms that require immediate emergency care typically begin three to seven days after the first signs of infection as the fever declines. They include severe abdominal pain or persistent vomiting; red spots or patches on the skin; bleeding from nose or gums; vomiting blood; black, tarry stools; drowsiness or irritability; pale, cold, or clammy skin; and difficulty breathing. No one in Key West has reached this level, Eadie said.