FRIDAY, Dec. 16 (HealthDay News) -- While the alarming
re-emergence in 2009 and 2010 of mosquito-borne dengue fever in the
continental United States seems to have subsided, that's no reason
to believe the potentially deadly infection won't be back, experts
The outbreak of the sometimes-excruciating viral illness
centered on southern Florida. Now, researchers have issued an
update on the situation for one locale in particular, Key West.
"We know now that Key West is a high-risk area for dengue and we could have ongoing dengue outbreaks again," said the report's lead author, Carina Blackmore, from the Florida Department of Health. However, if people use air conditioners and screens and stay inside during hot, muggy days there is little chance dengue will become endemic, she said.
Dengue remains a leading cause of illness and death in tropical
areas but was largely thought to be absent from the United States
since the 1950s.
However, in 2009, 27 people living in Key West came down with
illness via locally acquired infections, and then 66 more residents
contracted the illness in 2010, the researchers report. The
outbreak seems to have eased since then, with no cases reported in
That doesn't mean that dengue is eliminated from the population,
however, because around 75 percent of people infected never develop
symptoms. Blackmore and her colleagues estimate, therefore, that
about 5 percent of people living in Key West neighborhoods where
cases occurred could be infected.
Because Key West has a large population of the type of
mosquitoes that transmit dengue, called the "house mosquito,"
Blackmore's team decided to investigate the size of the outbreak
there. They identified a number of cases and found that people who
got dengue were less likely to use air conditioning, and they often
had birdbaths or other types of containers where the mosquitoes
Blackmore noted that dengue is not transmitted person to person,
but from humans to mosquitoes and then back to humans again.
However, trying to eradicate house mosquitoes has never been
successful, she said, because of where they tend to propagate.
"House mosquitoes are lazy mosquitoes -- they breed in [even] very
small containers," she said.
The report appears in the January issue of
Emerging Infectious Diseases, which is published by the U.S. Centers for Disease Control and Prevention (CDC).
Dr. Hal Margolis, chief of the CDC's dengue branch, said that
most dengue that appears in the United States is still brought back
by people who have traveled to areas in the world where the
diseases is endemic. "There are thousands of people who come back
with dengue. That's really the biggest problem," he said.
There are also sporadic outbreaks along the Texas/Mexican
border, Margolis said. In addition, dengue is endemic in some areas
of the United States such as Puerto Rico, the U.S. Virgin Islands
and Asian possessions such as Guam and American Samoa, he said.
The Key West outbreak was unusual in that it lasted for two
seasons, Margolis said. "Frankly, we don't know if it is still
there," he added. "How it got introduced, we don't know."
Dengue could still become endemic in Florida, Margolis said. "We
won't know for several seasons. Only time will tell us; it's really
had to predict," he said.
The disease can cause a high fever and people can feel sicker
than they have ever felt before, Margolis said. "The danger comes
in those people who get severe dengue; that usually happens with a
second or third infection," he said. "Twenty-five percent of people
who have first infections may go on to have severe dengue."
In severe dengue, plasma leaks out of the blood vessels, ending
up around the lungs and abdomen, and sufferers can develop shock,
Margolis said. About 15 percent of people have these severe signs,
he said. About 1 percent may die, he added.
The biggest hope for prevention lies with a vaccine, Margolis
"There is a lot of effort on dengue vaccines going on, but it's going to be another three or four years before a vaccine is approved," he said. There are vaccines currently in clinical trials, he added.
Trying to control the mosquitoes to curb infections has
not proven to be all that effective, he said. People who have
air conditioning or screened windows may be at lower risk, since a
closed house keeps the flying insects at bay.
Infectious disease expert Dr. Marc Siegel, an associate
professor of medicine at New York University in New York City,
agreed with the experts' warnings. "I wouldn't be surprised to see
more cases," he said.
The problem is that the mosquitoes in Key West are now carrying
the disease, which makes it more likely that there will be more
outbreaks, Siegel said.
For more information on dengue, visit the
U.S. Centers for
Disease Control and Prevention.
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