Climate Change and Infectious Disease

Of growing concern among public-health professionals is the way in which climate change may be advancing the spread of infectious disease. For example, 1999 saw the first North American outbreak of West Nile virus, a mosquito-borne tropical disease that killed seven people in New York City. The virus struck during a summer of droughts and prolonged heat waves following a mild winter-long-term weather phenomena associated with climate change.

The 1990s were the warmest decade of the last century; as areas heat up, warmth-loving mosquitoes can better infiltrate them. And warmer nights and winters may allow mosquitoes to live-and bite-for longer periods of time. Floods and droughts associated with climate change also can create breeding sites for mosquitoes, whose eggs and larvae need stagnant water. As floods recede, they leave puddles; during droughts, streams can become pools. In addition to West Nile virus, other diseases transmitted by mosquitoes, such as malaria, dengue fever, yellow fever and several kinds of encephalitis, are likely to become more prevalent and widespread as global temperatures increase.

Extreme weather shifts linked to climate change also heighten the risk of diseases. Greater frequency of severe rainstorms and floods could increase the amounts of pesticides, fertilizers and sewage that run off from farms, lawns and streets into the nation's warming water bodies. In addition to polluting water, this runoff could produce more frequent blooms of toxin-producing algae that contaminate fish and shellfish. And water-borne contagious diseases such as cholera, caused by a pathogen that grows on algae, could become more frequent, as could diseases spread through lack of clean drinking water.

To help prevent outbreaks, we need to be able to rapidly identify the emergence or resurgence of infectious diseases or the vectors that carry them. Some members of the public-health community have discussed the need for what they term "dual use" disease tracking, aimed at early detection of everything from epidemics of colds and flu to possible bioterrorist events. When there is an outbreak, the public should be quickly informed. With adequate warning of diseases such as cholera, for instance, people can filter their drinking water.

This summer, families can reduce the risk of mosquito-borne disease by eliminating standing pools of water on the ground and in drains and receptacles. If a disease, such as West Nile virus, is identified in an area, precautions should be taken: minimize time spent outdoors between dusk and dawn, when mosquitoes are most active, and wear shoes, socks, long pants and long-sleeve shirts outdoors. In the longer term, a sound prevention strategy against climate-linked diseases should include reducing our emissions of greenhouse gases and conserving and protecting our drinking water.

Dr. Landrigan is Director of the Center for Children's Health and the Environment (CCHE) at Mount Sinai School of Medicine in New York City. Anjali Garg is Health Policy Analyst at CCHE. See www.childenvironment.org, www.healthy-kids.com, for more information from CCHE.