Climate Change and Infectious Diseases

The "conventional wisdom," in the words of Lafferty (2009), "is that global climate change will result in an expansion of tropical diseases, particularly vector-transmitted diseases, throughout temperate areas," examples of which include "schistosomiasis (bilharzia or snail fever), onchocerciasis (river blindness), dengue fever, lymphatic filariasis (elephantiasis), African trypanosomiasis (sleeping sickness), leishmaniasis, American trypanosomiasis (Chagas disease), yellow fever, and many less common mosquito and tick-transmitted diseases of humans," as well as many diseases of "nonhuman hosts." But does this "wisdom" hold up well in the scientific literature?

In and effort to find out, Lafferty reviews the scientific literature pertaining to: (1) how temperature drives several important biological processes, (2) how changes in climate might affect the spatial and temporal patterns of infectious disease transmission, and (3) how models predict the ways in which climate change might affect the spread of infectious diseases in the future.

Based upon that review, the U.S. government researcher concludes that "while climate has affected and will continue to affect habitat suitability for infectious diseases, climate change seems more likely to shift than to expand the geographic ranges of infectious diseases," and that "many other factors affect the distribution of infectious disease, dampening the proposed role of climate." In fact, he concludes that "shifts in climate suitability might actually reduce the geographic distribution of some infectious diseases." And of perhaps even greater import (because it is a real-world observation), he reports that "although the globe is significantly warmer than it was a century ago, there is little evidence that climate change has already favored infectious diseases."

So, will global warming lead to dramatic increases in the incidence of various infectious diseases, as climate alarmists claim it will? Lafferty's review of pertinent biological phenomena suggests that it need not do so, while his review of real-world observations suggests that it has not done so. Hence, in all likelihood, it probably will not do so.