Global warming and malaria, another myth debunkedby Jonathan DuHamel on Jan. 04, 2012, under Climate change
Among the many scary scenarios attributed to a warming world is the claim that malaria will spread. But new research, reported in Nature says: “that warmer temperatures seem to slow transmission of malaria-causing parasites, by reducing their infectiousness.” The researchers say “that there are several possible explanations for why parasite survival falls as temperature increases: the parasite may not be able to cope with the higher temperatures, or mosquito immune systems may work better at warmer temperatures.” This seems to support an earlier paper in Nature that found, “widespread claims that rising mean temperatures have already led to increases in worldwide malaria morbidity and mortality are largely at odds with observed decreasing global trends in both its endemicity and geographic extent.”
Although malaria is often thought of as a tropical disease, it was actually much more widespread.
“It was an important cause of illness and death in the past century in Upper and Lower Canada and out into the Prairies.” -MacLean and Ward, Journal of the Canadian Medical Association, Jan. 26, 1999.
“Present global temperatures are in a warming phase that began 200 to 300 years ago. Some climate models suggest that human activities may have exacerbated this phase by raising the atmospheric concentration of carbon dioxide and other greenhouse gases. Discussions of the potential effects of the weather include predictions that malaria will emerge from the tropics and become established in Europe and North America. The complex ecology and transmission dynamics of the disease, as well as accounts of its early history, refute such predictions. Until the second half of the 20th century, malaria was endemic and widespread in many temperate regions, with major epidemics as far north as the Arctic Circle. From 1564 to the 1730s—the coldest period of the Little Ice Age—malaria was an important cause of illness and death in several parts of England. Transmission began to decline only in the 19th century, when the present warming trend was well under way. The history of the disease in England underscores the role of factors other than temperature in malaria transmission.” – Paul Reiter, Emerging Infectious Diseases, Vol. 6, No. 1, January–February 2000.
In the United States:
“Historically, malaria was a significant cause of morbidity and mortality throughout the western United States” as well as in the Mississippi, Ohio, and Missouri river valleys and along the Atlantic coast. -Hayden et al. Journal of Medical Entomology, vol. 38, no. 2, pp. 341-343, 2001.
Malaria has largely disappeared from temperate climes through economic development and disease control. Recent warming seems to have had no effect. However, malaria remains a scourge in many undeveloped areas, a scourge made worse by another environmental policy: the banning of DDT, but that’s another story.