(Agencies)
Updated: 2007-09-19 16:14

CHICAGO - Global warming likely will lead to an increase in infectious disease around the world, as viruses, microbes and the agents that spread them flourish, experts at a medical conference warned Tuesday.

The problem is already evident and has become particularly acute in just the past decade, according to researchers at a meeting of the American Society for Microbiology.

"Years ago we probably would not be talking about this topic," said Anthony McMichael, lead scientist on a study entitled "The Impact of Climate Change on Human Health."

"Human-induced climate change ... is proceeding a little bit faster than we would have expected," said McMichael, an epidemiologist at the University of Canberra in Australia.

Experts cite West Nile virus as a disease whose spread has been facilitated by global warming.

Native to Africa, West Nile can be found today throughout Canada and the United States, according to McMichael, who explained that a rise in North American temperatures since 1999 has allowed non-native mosquitoes that transmit the virus to thrive.

Jim Sliwa, spokesman for the American Society for Microbiology, underscored the potential health crisis posed by a rise in world temperatures.

"We know that climate change is going to change the pattern of infectious diseases," said Sliwa at the conference, which, with some 12,000 physicians and scientists, is billed as the world's biggest on disease-causing microbes.

For example, he said, "the malaria line in mountainous regions will continue to rise," as global average temperature increases.

McMichael also predicted a rise in the incidence of "year-round influenza" in the tropics.

Near the equator, he said "there is no influenza season, so as the temperature rises the tropical areas expand and we'll get more year-round influenza."

Climate change experts believe that the earth's temperature is likely to rise by 1.8-4.0 degrees Celsius by the year 2100.

Experts believe diseases worsened by global warming already have contributed to the deaths of between 150,000 and five million people per year.

In addition to an increase in diseases like malaria and dengue fever, global warming is likely heighten the incidence of diarrhea, heat waves, drought, floods and malnutrition.

To prevent a global warming drive health crisis, McMichael said, researchers will have to begin to think about the interconnectedness of climate and infectious diseases.

"We are going to have to think within larger integrated terms (and) employ a more ecological perspective," he said at the conference, which runs through Thursday.

However, McMichael said there are some areas where infectious disease may be less virulent as a result of global warming.

"In West Africa, for example, the rate of (malaria) is likely to decline, as future conditions are getting too hot and too dry for the mosquito," he said, adding that there has been a 25 percent decline in rainfall over the last three decades in the Sahara region of Africa.

"Sub-Saharan Africa almost certainly is in an early stage of a climate change process which we know is tending to displace rainfall systems," McMichael said.