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Thursday, 21 September, 2000, 00:45 GMT 01:45 UK
Warming 'not spreading malaria'
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Warming has implications for disease transmission
A leading insect expert has poured cold water on the theory that global warming may be behind the spread of malaria.

In recent years, some researchers have noticed increases in malaria cases in countries outside the tropics, traditionally viewed as the epicentre of the disease.

In addition, malaria has increased in cooler highland regions of some African countries such as Kenya and Rwanda.

But Paul Reiter, chief entomologist at the US Government's dengue research laboratory in Puerto Rico, says climate change is not to blame.

He pointed out, in an interview with New Scientist magazine, that virtually all of the US was plagued by malaria in the 1880s, and that the disease had been endemic as far north as Finland.

He said: "At times, the disease has been rampant - indeed, the world's first recorded epidemic was in Philadelphia in 1780."

"Specialists in my field have had little voice in this debate. Take the Intergovernmental Panel on Climate Change (IPCC) which produced a global assessment in 1996.

"The bibliographies of the nine lead authors of the health section show that between them they had only published six research papers on vector-borne diseases.

Predator paradise

"Nevertheless, they devoted a third to a half of their chapter to speculation on the future of those diseases."

He disputes the theory that mosquito predators would be vulnerable to the effects of climate change: "Longer warm seasons could lead to higher, more stable predator populations."

And he blames a combination of forest clearance, population explosion - forcing people to cultivate land more prone to mosquitoes - increased travel, and resistance to anti-malarial drugs for much of the increase recorded in some African countries.

He added: "Perhaps the most important factor in Rwanda is that from 1984 to 1988 Unicef and other organisations spent several million dollars to improve malaria surveillance and control.

"When you improve surveillance, you get more recorded cases."

He said that using the malaria argument to force action on climate change was wrong. "My interest is trying to keep the science straight."

One of the proponents of the idea that global warming could increase the threat from diseases such as malaria and dengue fever in the future is Tony McMichael, professor of epidemiology at the London School of Hygiene and Tropical Medicine.

But he said: "There may or may not have been recent influence of climate change but if there has been, we certainly can't detect it against the background noise.

"It's well accepted by vector disease biologists that if climatic conditions were to change, it would alter the probability of disease transmission.

"Whether or not that probability is realised will be hugely influenced by the prevailing social and economic conditions."

He told a conference: "Global warming has already caused a marginal change in the last decade. We are getting into an unfamiliar and hazardous world."

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19 Feb 00 | Washington 2000
'Death by global warming'
23 Jun 99 | Sci/Tech
Tell-tale signs of climate change
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