29 December 2008

Dengue, Typhoid, and Cholera Cases in 2008

I believe in global warming and why an increase in average temperature can contribute to an increase in the number of possible dengue cases annually. As early as 1998, scientists were already predicting this scenario:
The geographic range of Ae. aegypti (mosquito carrier of dengue) is limited by freezing temperatures that kill overwintering larvae and eggs, so that dengue virus transmission is limited to tropical and subtropical regions. Global warming would not only increase the range of the mosquito but would also reduce the size of Ae. aegypti's larva and, ultimately, adult size. Since smaller adults must feed more frequently to develop their eggs, warmer temperatures would boost the incidence of double feeding and increase the chance of transmission.

In addition, the time the virus must spend incubating inside the mosquito is
shortened at higher temperatures. For example, the incubation period of the dengue type-2 virus lasts 12 days at 30 C, but only seven days at 32-35 C. Shortening the incubation period by five days can mean a potential three-fold higher transmission rate of disease. - ScienceDaily, March 1998

Then again, one would wonder why neighboring Cambodia had fewer dengue cases in 2008:

As for cholera and typhoid, poor sanitation practices are the most common causes for transmission. Simple hand washing and proper food handling remain some of the best preventive measures to avoid getting these diseases. But sanitation and hygiene are difficult to enforce in a country where most do not own decent toilets and where cleanliness is not always next to godliness.

Cholera, dengue, and typhoid are all preventable diseases. Global warming will happen, and most people might have little control over its true outcome, but adapting preventive healthy sanitation measures can do a lot to stop future disease cases from happening or increasing.
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