Global Warming Increases Risk of Disease: Study

"Just a one- or two-degree change in temperature can lead to disease outbreaks"
 

WASHINGTON (AP)

Saturday, June 22, 2002

A warming climate will allow disease-causing pathogens to thrive in places where they once could not live, posing a new risk for species as diverse as butterflies and humans, oysters and lions, a study suggests.

In research published Friday in the journal Science, researchers say that bacteria, bugs, parasites, viruses and fungi that have been restricted by seasonal temperatures may be able to invade new territories and find new victims as the climate warms and winters grow milder.

"Climate change is disrupting natural ecosystems in a way that is making life better for infectious diseases," said Andrew Dobson, a Princton University researcher and a co-author of the study. "The accumulation of evidence has us extremely worried. We share diseases with some of these species. The risk for humans is going up."

Climate changes already are thought to have contributed to an epidemic of avian malaria that wiped out thousands of birds in Hawaii; the spread of an insect-borne pathogen that causes distemper in African lions; and the bleaching of coral reefs attacked by diseases that thrive in warming seas.

Humans are also at direct and dramatic risk from such insect-borne diseases as malaria, dengue and yellow fever, the researchers said.

"In all the discussions about climate change, this has really been kind of left out," said Drew Harvell, a Cornell University marine ecologist and lead author of the study. "Just a one- or two-degree change in temperature can lead to disease outbreaks."

In the study, the authors analyzed how arming temperatures already are letting insects and microbes invade areas where they once were killed by severe seasonal chills. They said mosquitoes are moving up mountainsides, spreading disease among animals formerly protected by temperature. They also found some pathogens, reproduce more often in warmer temperatures, so there are more germs around to cause infection.

Among the possible effects they found:

Epidemics of Rift Valley fever, a deadly mosquito-borne disease, rage through northeastern Africa during years of unusual warmth. If the climate becomes permanently warmer and wetter, as some predict, Rift Valley fever epidemics will become frequent.

Malaria and yellow fever may become more common as milder winters permit the seasonal survival of more mosquitoes, which carry these diseases. A warmer climate also could enable them to move into areas where the cold once kept them out.