Scientists Alarmed at New Disease Epidemics

by Cat Lazaroff, ENS

The changing, warming climate around the globe is triggering unprecedented numbers of disease outbreaks in both land- and ocean-based wildlife populations, from coral reefs to rainforests. Ecologists and epidemiologists express concern over this rising trend in the June 21 issue of the journal Science. The two-year study, developed by the National Center for Ecological Analysis and Synthesis (NCEAS) is the first to analyze disease epidemics across entire plant and animal systems, on land and in the oceans. The study investigates the outbreaks in relation to temperature.

"What is most surprising is the fact that climate-sensitive outbreaks are happening with so many different types of pathogens--viruses, bacteria, fungi and parasites--as well as in such a wide range of hosts including corals, oysters, terrestrial plants, birds and humans," said lead author Drew Harvell of Cornell University. Said coauthor Richard Ostfeld from the Institute of Ecosystem Studies in Millbrook New York. "We don't want to be alarmist, but we are alarmed."

"Climate change is disrupting natural ecosystems in a way that is making life better for infectious diseases," said epidemiologist Andrew Dobson of Princeton University. "The accumulation of evidence has us extremely worried. We share diseases with some of these species. The risk for humans is going up." As temperatures increase, these carriers are likely to spread into new areas and may have potentially devastating effects on wildlife populations that have not been previously exposed. Reproduction, growth, and biting rates of insects all go up with increases of temperature.

Winter is the limiting time for many pathogens, killing populations each year, but milder winters are removing this barrier. Warmer, longer summers also mean that the period of time of disease transmission is longer. Dobson warned, "It's not only going to be a warmer world, it's going to be a sicker world." Marine bacteria and fungal growth rates are both linked to increasing temperatures. During the unusually warm 1998 El Nino year, corals suffered massive die offs worldwide. A new large bleaching event has just occurred in Australia.

In the Hawaiian Islands, mosquitoes are now spreading malaria into the last populations of honeycreepers, boldly colored songbirds that evolved only in Hawaii. In the 1960s, mosquitoes were restricted by temperature to elevations below 2,500 feet, but warmer temperatures have allowed them to move higher up the mountainsides. "Today there are no native birds below 4,500 feet," said Dobson. Humans and animals are affected by spreading diseases as well. In the wetter conditions, mosquito populations explode and more mosquitoes acquire the disease and transmit it.

For more information on taking personal precautions against mosquito-borne illnesses such as West Nile virus and how to mosquito proof your home, visit www.nyc.gov/html/doh/html/wnv/wnvhome.html To contact your state health department about West Nile virus, log on to: www.cdc.gov/ncidod/dvbid/westnile/city_states.htm