Wednesday, July 27, 2016

More Mosquito Days Increasing Zika Risk in U.S.

Published: July 27th, 2016

Hot and humid summer weather across the U.S. brings with it the rise of the mosquito season, and this year the threat of the Zika virus makes that more than a minor nuisance. Mosquito species found in the Lower 48 states are known to transmit this disease, thriving in tropical and subtropical climates. As the climate warms and humidity increases across the nation, the risk of mosquito-borne diseases, like Zika, is becoming more prevalent for Americans.


Nationwide, 76 percent of major cities have seen their mosquito season grow over that time.

Analysis based on ideal climate conditions for Asian Tiger Mosquitoes: between 50-95°F and relative humidity greater than 42%.

Climate Central’s States at Risk project has analyzed how the length of the mosquito season has been changing across hundreds of metropolitan areas across the Lower 48 states. We found that in most of the country, rising temperatures and humidity since the 1980s have driven an increase in the number of days each year with ideal conditions for mosquitoes. Warming temperatures lead to more evaporation, which puts more water vapor in the atmosphere and increases humidity. The overall increase in mosquito days in the U.S. is likely increasing the risk of several mosquito-borne diseases, including the Zika virus.

Cities like Baltimore and Durham, N.C., have seen their annual average mosquito season grow by nearly 40 days since the 1980s.

Dozens of cities across the Midwest, Northeast, and along the Atlantic Coast have all seen their mosquito seasons grow by at least 20 days over the past 35 years.

More than 20 major U.S. cities have ideal climate conditions for mosquitoes at least 200 days each year.

In a few hot Southern cities, rising extreme heat since the 1980s has actually caused the mosquito season to begin to decrease (though there are still hundreds of days each year with ideal conditions for mosquitoes in these locations).


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