July 8, 2009 / 7:30 PM / in 8 years

Climate change could boost U.S. dengue fever cases

WASHINGTON (Reuters) - Climate change could push dengue fever into all corners of the United States, as the mosquitoes that can carry the traditionally tropical virus survive warmer U.S. winters, researchers said on Wednesday.

Known colloquially as breakbone fever for the aching bones that are one symptom of the disease, dengue fever can be treated effectively with bed rest and liquids, but it often goes undiagnosed in the United States.

Two species of mosquitoes capable of transmitting dengue fever have been spotted in 28 states and Washington D.C., according to a report by the Natural Resources Defense Council. Cases of the disease have been reported in every U.S. state, but many of those are so-called imported cases where the patient was infected by mosquitoes elsewhere in the world.

Dengue fever, a long-standing problem in tropical areas, was until recently rare in most of the United States, except along the Texas-Mexico border. That could be changing due to a range of factors including global warming, scientists at the Natural Resources Defense Council said in a report.

As few as 10 percent of U.S. dengue infections are correctly diagnosed, Kim Knowlton, one of the report’s authors, said by telephone.

“Because there has been, up to this point, the perception that it’s a tropical concern, we think it’s not been on the radar of many clinicians,” she said.

“Rising temperatures do affect the range of these two mosquito vectors, to the extent that warming winter temperatures can allow mosquitoes to overwinter more successfully and therefore be able to survive in new parts of the country,” Knowlton said.

Nearly 4,000 cases of imported and locally transmitted dengue fever were reported in the United States by the Centers for Disease Control and Prevention between 1995 and 2005; if cases along the Texas-Mexico border area are included, that number rises to 10,000.

“As temperatures rise, the potential for transmission may increase in vulnerable parts of the United States, as warmer temperatures and changing rainfall conditions expand both the area suitable for the mosquito vectors and the length of the transmission season,” the report said.

About 173.5 million U.S. residents live in counties with one or both of the mosquito species that can transmit dengue fever, according to the report.

Worldwide, dengue fever and its complications cause 50 to 100 million infections and 22,000 deaths annually in more than 100 countries.

By 2085, an estimated 5.2 billion people are projected to be at risk for dengue due to rising temperatures and humidity spurred by climate change, the report said.

More information is available online at www.nrdc.org/health/dengue/

Editing by Cynthia Osterman

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