February 6, 2008
Climate Change and the Spread of Disease
Slate.com has an interesting piece discussing the what impact, if any, climate change may have on the spread of various diseases. Maria Said writes,
Before the summer of 2007, Castiglione di Cervia, Italy, was known as a quiet village near Ravenna. In July, however, doctors noticed complaints of excruciating joint pain, fever, headaches, and rash. Their patients were experiencing a fever called "chikungunya"; the word originates in the Makonde language in Tanzania and Mozambique and means "to dry up or become contorted." This epidemic had two years previously raged unexpectedly through islands in the Indian Ocean. But it was new to Europe.
And so Castiglione found itself at the center of scientists' efforts to map the effect of climate change on the spread of infectious disease. In December, at a Washington, D.C., conference sponsored by the Institute of Medicine, scientists and doctors wrestled with these questions: Did global warming bring chikungunya to Italy? Will it lead to a return of scourges like malaria, pushed out of Europe and the United States in the mid-20th century? Will epidemics worsen in poorer countries? . . . .
While they readily accept the associations between climate and infectious agents, scientists balk at stating exactly what a change in climate might cause. This reluctance lies both in the complexity of disease and in the nature of science, in the need to build a case incrementally, fact by fact. Asking a scientist to predict the spread of disease is like asking him or her, while standing in the midst of a tornado, to predict how the landscape will change by measuring the direction and amount of debris flying by.
Take the chikungunya debate: Initially hailed as a clear example of how warmer weather can lead to new epidemics, some experts pointed out that it was not global warming but a new mutation of the virus that made the fever increasingly infectious. Others argued that the reasons for the chikungunya epidemic lay in new routes for disease opened up by the global economy; in the 1990s, imported tires carried into Italy a mosquito known as "the Asian tiger," which can serve as a vector for chikungunya as well as dengue fever. . . . .
What is the alternative to endless discussion? Recent editorials in the New England Journal of Medicine and the Lancet call for accepting, even without 100 percent certainty, the accumulating body of evidence that climate change will affect infectious diseases. Doctors regularly make recommendations to patients based on what they think might happen. Gina Solomon, a physician and senior scientist for the Natural Resources Defense Council, points out that not knowing whether hypertension will hurt an individual patient does not stop a doctor from trying to bring his or her blood pressure down.
A different slant, put forth by Peter Schwartz and others at the consulting agency Global Business Network, sidesteps the need for scientific proof. Their "systems vulnerability approach" does not try to predict what will happen to the climate; rather, it identifies existing vulnerabilities in our world that could easily tip a region toward a new epidemic given the additional stress of climate change. A damaged Iraqi town without a clean water source is more vulnerable to a cholera outbreak if waters there warm, as they did in Peru. An unusually hot summer in a sprawling slum in Mexico City becomes the breeding ground for an epidemic of infectious diarrhea. We may not know precisely what causes what. But we don't have to sit back and wait to see what the weather will do.
February 6, 2008 | Permalink
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