What will climate change mean for infectious disease?

Projecting the impact of global environmental change on patterns of infectious disease is not simply a matter of plotting a rise in predicted temperature change and correlating that with the temperature and geographic range of a pathogen. Disease resides within a complex ecosystem, natural and manmade, which influences whether and how it might become manifest. Our knowledge of these systems is frustratingly limited and incomplete.

As an example, many tropical diseases are temperature dependent for both the pathogen and its vector, often mosquitoes. They thrive only above a certain threshold, speeding their lifecycle as the temperature rises. “It can have a huge difference on [sic] transmission dynamics,” says Jonathan Patz, director of the Global Health Institute at the University of Wisconsin.

Researchers have compared mosquito maturation in huts in forested areas with their maturation in huts in deforested areas. The difference in temperature was just a few degrees but the percent of insects that transitioned from larva to adulthood jumped from 65% to 82%, and the time to development was cut from 9 to 8 days. According to Patz, the result was a much greater population of mosquitoes to transmit malaria, dengue, or other diseases.

No single factor alone can explain much says David Relman, a professor of microbiology and immunology at Stanford University. He leads an Institute of Medicine panel that is revisiting questions of climate change and disease. He says that myriad biological, ecological, social, and human factors interweave to shape and reshape disease dynamics, each modulated by unique combinations of local factors.

West Nile virus in the United States is an example of how a disease might establish …