A woman has been diagnosed in Las Vegas with dengue fever, a potentially fatal mosquito-borne disease that is not spread person to person.
There is no evidence to suggest the local population has anything to worry about, said Jennifer Sizemore, a spokeswoman for the Southern Nevada Health District.
"We were able to confirm this morning that we have received a report of a case of dengue fever," Sizemore said Monday.
"This person had a travel history to indicate she got it outside of the U.S.," she said. "There is no evidence that there was a transmission locally."
The health district declined to identify the woman or say which country she recently visited, or even which hospital treated her.
Dengue fever is rare in the continental United States but not as rare as it used to be. Several cases have been reported in Florida and two in Virginia in recent months.
And the Asian tiger mosquito -- an aggressive carrier of dengue fever -- was found in Southern California this month.
Worldwide, 50 million to 100 million people contract the disease each year, mainly in tropical and subtropical regions of the planet where mosquitoes thrive. More than 1,000 people have contracted the disease in Pakistan, and at least 100 of them have died.
Another outbreak is ongoing in the Bahamas.
There are four strains of the fever, said Professor Grayson Brown, director of the Public Health Entomology Laboratory at the University of Kentucky.
Brown said a person who survives a bout with one of the strains is immune after recovery but more susceptible to contracting any of the other three.
Dengue hemorrhagic fever and dengue shock syndrome both have a high fatality rate if not treated early and effectively, Brown said. The woman who was diagnosed in Las Vegas contracted a less serious strain.
DISEASE GOT FOOTHOLD IN U.S. IN 2010
Brown said the disease scratched out a foothold in the United States in 2010, after a large-scale outbreak occurred in the Caribbean. Several cases were first reported in the Florida Keys, and the disease spread throughout Florida, from Broward County in south Florida north to the Orlando and Jacksonville areas.
The Florida outbreak was the first in the United States in more than half a century, according to the federal Centers for Disease Control and Prevention in Atlanta.
"There was no effort to contain it, and our computer models demonstrate they can move far north," Brown said. "Once they're out of Florida, they can (spread) as far north as Tennessee and as far west as east Texas."
HOW FEVER SPREADS
Dengue cannot be spread directly from person to person, but one can get the disease by sharing a needle with someone who has been infected.
But a human with the fever can infect a mosquito in an area where dengue never existed before, and that mosquito would be a carrier in roughly a week, potentially triggering an outbreak.
Mosquitoes that carry dengue fever can carry the West Nile virus. But unlike West Nile, which causes problems for older people and those with compromised immune systems, dengue fever is "much worse," Brown said.
"You can be in great health and still be susceptible to dengue," he said.
The Southern Nevada Health District took a proactive approach to containing West Nile, which has seen some success since the virus first came to Southern Nevada several years ago. Neither dengue nor West Nile can survive through a winter here.
That bodes well in assessing what long-term threats are presented by the spread of dengue fever. The same measures residents and local authorities have undertaken to mitigate West Nile will help keep dengue fever at bay, health officials said.
The health district handles mosquito eradication on public property, and independent code enforcement offices in Clark County and local cities address mosquito havens on private property.
To minimize the risk, officials recommend people eliminate all sources of stagnant water on their property -- barrels, tires or "just about anything that holds liquid," Brown said.
Residents are asked to report green swimming pools, which have been abandoned or ignored by residents, making conditions perfect for mosquitoes to breed. Such pools have become commonplace throughout Southern Nevada because of the high number of foreclosed homes.
Contact reporter Doug McMurdo at dmcmurdo@ reviewjournal.com or 702-224-5512.