气候变化影响传染病传播

Climate change is affecting the spread of infectious diseases worldwide, according to an international team of leading disease ecologists, with serious impacts to human health and biodiversity conservation. Writing in the journal Science, they propose that modeling the way disease systems respond to climate variables could help public health officials and environmental managers predict and mitigate the spread of lethal diseases. The issue of climate change and disease has provoked intense debate over the past decade, particularly in the case of diseases that affect humans, according to the University of Georgia's Sonia Altizer, who is the study's lead author.

"For a lot of human diseases, responses to climate change depend on the wealth of nations, healthcare infrastructure and the ability to take mitigating measures against disease," said Altizer, an associate professor in the UGA Odum School of Ecology. "The climate signal, in many cases, is hard to tease apart from other factors like vector control and vaccine and drug availability."

Climate warming already is causing changes in diseases affecting wildlife and agricultural ecosystems, she said. "In many cases, we're seeing an increase in disease and parasitism. But the impact of climate change on these disease relationships depends on the physiology of the organisms involved, the location on the globe and the structure of ecological communities."

At the organism level, climate change can alter the physiology of both hosts and parasites. Some of the clearest examples are found in the Arctic, where temperatures are rising rapidly, resulting in faster developing parasites. A lungworm that affects muskoxen, for instance, can now be transmitted over a longer period each summer, making it a serious problem for the populations it infects.

"The Arctic is like a 'canary（金丝雀） in the global coal mine,'" said co-author Susan Kutz of the University of Calgary and Canadian Cooperative Wildlife Health Centre.

"Climate warming in the Arctic is occurring more rapidly than elsewhere, threatening the health and sustainability of Arctic plants and animals, which are adapted to a harsh and highly seasonal environment and are vulnerable to invasions by 'southern' species -- both animals and parasites."

A changing climate also is affecting entire plant and animal communities. This is particularly evident in tropical marine environments such as the world's coral reef ecosystems. In places like the Caribbean, warmer water temperatures have stressed corals and facilitated infections by pathogenic fungi and bacteria. When corals -- the framework builders of the ecosystem -- succumb（屈服）, the myriad of species that depend on them are also at risk.

"Biodiversity loss is a well-established consequence of climate change," said coauthor Richard Ostfeld of the Cary Institute of Ecosystem Studies. "In a number of infectious disease systems, such as Lyme disease and West Nile virus, biodiversity loss is tied to greater pathogen transmission and increased human risk. Moving forward, we need models that are sensitive to both direct and indirect effects of climate change on infectious disease."

Where human health is concerned, there is not only the direct risk from pathogens like dengue, malaria and cholera（霍乱）, all of which are linked to warmer temperatures, but indirect risks from threats to agricultural systems and game species crucial for subsistence and cultural activities.

"Earth's changing climate and the global spread of infectious diseases are threatening human health, agriculture and wildlife. Solving these problems requires a comprehensive approach that unites scientists from biology, the geosciences and the social sciences," said Sam Scheiner, National Science Foundation program director for the joint NSF-National Institutes of Health Ecology and Evolution of Infectious Diseases Program.

The study was funded in part by the National Science Foundation.