While it seems that a feared expansion of malaria due to a warming climate hasn't happened (and the reasons why
are a matter of much debate), there is renewed concern with the zika virus outbreak that other mosquito borne diseases are spreading faster because of the increased range (and life span?) of mosquitoes. As explained in this
Vox article, there are pretty good reasons to suspect a warming, wetter climate is already playing a role:
The spread of Zika is part of an unnerving trend: Several
mosquito-borne tropical illnesses have lately been spreading into
regions of the world that have never experienced them.
A viral disease called chikungunya — which had never appeared in the
Western Hemisphere until 2013 — has lately affected Central and South
America, even making an appearance in Florida last year. (Its name comes
from the Makonde language of Tanzania, where it was discovered in 1952;
it means "that which bends up," referring to the contorted physique of a
person afflicted by the virus.)
Dengue fever, known as "breakbone fever," has also seen new outbreaks
in Puerto Rico, Florida, Gulf Coast states, and Hawaii — all places
that hadn't usually been affected. In 2015, Brazil reported nearly 1.6
million dengue cases, a big increase from 569,000 in 2014.
Zika, dengue, and chikungunya are all spread by a species of mosquito called Aedes (in particular the Aedes aegypti and Aedes albopictus
mosquitoes). For reasons researchers don't understand, these mosquitoes
have been more effective at bringing diseases to new places lately,
affecting fresh populations that don't yet have the antibodies to fight
off the viruses.
Heidi Brown, a professor of epidemiology at the University of
Arizona, explained there are at least three factors that help these
illnesses spread: the number of mosquitoes out there, the number that
are biting humans infected with the virus, and the number that are
surviving long enough to infect other humans.
"The survival of the mosquito is driven a lot by temperature," she
added. Mosquitoes thrive in warm and moist environments. "So people go
to the idea of global warming — that climate change and changes in
precipitation patterns and temperature are helping mosquitoes survive in
different areas." In other words, warming is helping expand the range
of places that are habitable to mosquitoes.
There are other factors that may be driving the trend, too: People
are traveling more than ever, bringing diseases to new locales. More and
more people live in crowded cities, where it's easy for viruses to jump
from person to person and for mosquitoes to find large concentrations
of humans to feast on.
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