Nothing to fear from tropical diseases

by William Yeatman on March 30, 2004

in Science

The invaluable, run by Drs. Sherwood, Craig, and Keith Idso, draws attention this month to two important articles on the reality behind the supposed spread of tropical diseases in a warmer world.

First, Reiter et al. (in Emerging Infectious Diseases 9) examine the response of dengue fever in a significant outbreak in Laredo, Texas and Nuevo Laredo, Mexico in 1999. As summarizes, they learned that, “The incidence of recent cases, indicated by immunoglobulin M antibody serosurvey, was higher in Nuevo Laredo [16.0% vs. 1.3%], although the vector, Aedes aegypti, was more abundant in Laredo [91% vs. 37%].  Reiter et al. additionally determined that environmental factors that affect contact with mosquitoes, such as air-conditioning and human behavior, appear to account for this paradox.  They found, for example, that the proportion of dengue infections attributable to lack of air-conditioning in Nuevo Laredo [where only 2% of the homes had central air-conditioning compared to 36% of the homes in Laredo] was 55%, which means that 55% of the cases of dengue in Nuevo Laredo would not have occurred if all households there had had air-conditioning.” summarizes, “Reiter et al. correctly conclude, for example, that if the current warming trend in world climates continues, air-conditioning may become even more prevalent in the United States, in which case, the probability of dengue transmission [there] is likely to decrease [our italics].  And if the economy of Mexico continues to grow (which it will, if its citizens are allowed to freely utilize fossil fuels), the use of air-conditioners will likely gain momentum south of the border, which would lead to even greater decreases in the occurrence of dengue there.

“Clearly, the development of wealth, which currently is dependent on the availability of fossil-fuel-derived energy, will lead to greater decreases in mosquito-borne diseases than any change or stasis of climate ever would.”

The other article, Small et al. (Proceedings of the National Academy of Sciences 100), looks at the impact of climate change on malaria transmission in Africa. According to the Idsos, the researchers “determined that malaria transmission suitability did indeed increase because of climate change in specific locations of limited extent; but in Southern Mozambique, which was the only region for which climatic suitability consistently increased, the cause of the increase was increased precipitation, while areas where the climate became less suitable for malaria transmission had all experienced decreased rainfall.  In fact, Small et al. say that climate warming, expressed as a systematic temperature increase over the 85-year period, does not appear to be responsible for an increase in malaria suitability over any [our italics] region in Africa.”

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