The Weakest Link, Goodbye
by Howard Fienberg
It is often said that a warming world will lead to greater
epidemics of infectious diseases like
So why do infectious disease researchers appear so
disinterested in global warming? Because their research does not indicate any
simple link between global climate changes and the spread of infectious
disease. For instance, a new article in the journal Nature (Feb. 21)
examining malaria could find no association whatsoever.
What else could have caused the uptick in malaria? At
Kericho, the researchers point to the growth of anti-malarial drug resistance
(those drugs having been the public health response to the large epidemics
sixty-some years ago). Similarly, drug resistance, rather than climate
changes resulting from local deforestation, seems a more likely culprit in
the Usambara mountains of
Across other highland African areas, “increases in
malaria have been attributed to population migration and the breakdown in
both health service provision and vector control operations.” The
researchers conclude that, given the climate variability in
Changes in the weather can have dramatic impacts on diseases and the pests that spread them. However, as the Nature study hints, and a report from the National Research Council pointed out last year (“Under the Weather”), the relationship traditionally drawn between climate and disease can be misleading.
Other influences, such as ecological, biological and societal changes, can have an even greater impact. Malaria and dengue outbreaks might be caused by anything from deforestation to population increases. And thanks to increased globalization, diseases can be transported worldwide in a matter of hours.
This does not mean that the climate has no impact. The life cycles of many disease pathogens and vectors are directly or indirectly influenced by changes in temperature, precipitation and humidity, affecting “the timing and intensity” of outbreaks. Unfortunately, most of the links made between climate and disease result from computer models.
Computers can calculate anything, but effectively including all relevant factors in a climate model is no easy feat. Inevitably, computer climate models only capture part of the story of infectious diseases. The NRC cautioned that such models are good for some kinds of analyses, but “are not necessarily intended to serve as predictive tools,” since they cannot “fully account for the complex web of causation that underlies disease dynamics.”
The NRC report stressed that there are a lot more possible influences than climate, including “sanitation and public health services, population density and demographics, land use changes, and travel patterns.” So strong public health measures “such as vector control efforts, water treatment systems, and vaccination programs” remain the most effective weapons in the battle against infectious disease.
Centers for Disease Control entomologist Paul Reiter thinks
that North Americans and Europeans have forgotten that malaria and dengue are
not just tropical diseases (New Scientist, Sep. 23, 2000). In the 1880's,
malaria existed in most of
It would be a shame if our misperceptions prevented us from properly dealing with infectious diseases, which kill millions of people worldwide every year. Global warming may or may not be a disaster waiting to happen, but lumping it together with more tangible public health problems probably wont help solve either one.
See the original: http://www.tcsdaily.com/article.aspx?id=032502A
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