engue (or breakbone) fever is a prolonged, severe flu-like illness which in certain forms can be fatal. Unlike yellow fever (caused by a related virus and spread by the same mosquito) there is no vaccine for dengue fever.

The mosquitoes that carry dengue fever (Aedes aegypti) are limited by temperature. Frost kills adults and larvae. Temperature measurements have detected a 1.5° C rise since 1970 in the freezing level in tropical mountains, further evidence of the global warming trend recorded by meteorologists during the past century. Glaciers are also retreating on six continents and upward migration of plants has been widely observed. Global warming is projected to significantly increase the range conducive to the transmission of both dengue and yellow fever. As if to confirm these predictions, dengue fever has been recently reported at higher elevations than before, at 1240 meters in Central America, 1700 meters in Mexico and 2200 meters in the Colombian Andes. Following a Mexican epidemic, 3 cases of dengue fever were reported in Texas in October 1995.