for National Geographic News
Climate change is accelerating the spread of dengue fever throughout the Americas and in tropical regions worldwide, researchers say.
More rainfall in certain areas and warmer temperatures overall are providing optimal conditions for mosquitos—which spread the virus that causes dengue—to breed and expand into new territories.
By 2085 climate change will put an estimated 3.5 billion people at risk of dengue fever, the United Nations's Intergovernmental Panel on Climate Change (IPCC) said in March. (Related news: "Dengue Fever: Growing Threat Rivals Malaria, Ebola, Experts Say" [October 18, 2006].)
"Climate change is incurring lots of unintended consequences for health around the world," said Paul Epstein, associate director of the Center for Health and the Global Environment at the Harvard Medical School. Epstein also worked on the IPCC report.
The upsurge in dengue, the world's most widespread vector-borne virus, is part of this wider trend.
For instance, heat waves and heat-related illnesses and death, an increase in incidence of tropical diseases, and a rise in tick-borne Lyme disease are all becoming a reality, Epstein said.
Dengue in the Americas
Dengue—which is usually not fatal—is most commonly spread by the Aedes aegypti mosquito, a domestic, day-biting insect that favors human blood.
Dengue transmission is largely confined to tropical and subtropical regions, since freezing temperatures kill the mosquito's larvae and eggs.
Dengue's burden may be most serious in the American continents, according to the U.S. Centers for Disease Control and Prevention.
The number of cases reported in the Americas increased from 66,000 in 1980 to 552,000 in 2006, according to the Pan American Health Organization. Brazil, Paraguay, and the Dominican Republic have all had serious epidemics in recent years.
And in Mexico dengue cases have increased by more than 600 percent since 2001, according to Mexico's National Center for Epidemiology and Disease Control.
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