Washington, Sept 23 : Climate change is accelerating the spread of dengue fever throughout the Americas and in tropical regions worldwide, a new study by a Harvard Medical School researcher has revealed.

The study said more rainfall in certain areas and warmer overall temperatures was providing optimal conditions for mosquitoes –which spread the virus that causes dengue – to breed and expand into new territories.

The study also cited the UN’s Intergovernmental Panel on Climate Change (IPCC) report, which says, that by 2085, climate change would put an estimated 3.5 billion people at risk of dengue fever.

“Climate change is incurring lots of unintended consequences for health around the world,” National Geographic quoted Paul Epstein, associate director of the Center for Health and the Global Environment at the Harvard Medical School, as saying.

He said, heat waves and heat-related illnesses and death, an increase in incidence of tropical diseases, and a rise in tick-borne Lyme disease were all becoming a reality.

Dengue, which is usually not fatal – is most commonly spread by the Aedes aegypti mosquito, a domestic, day-biting insect that favours human blood.

Dengue transmission is largely confined to tropical and subtropical regions, since freezing temperatures kill the mosquito's larvae and eggs. (With inputs from ANI)