Global climate change is expected to contribute
to the worldwide burden of disease and premature deaths. Scientists predict that rising average temperatures in some regions will change the transmission dynamics and geographic range of cholera
, dengue fever
, and tick-borne diseases. Increased precipitation may raise the number and productivity of breeding sites for vectors
such as mosquitoes, ticks, and snails. Rising atmospheric and surface temperatures are also increasing the intensity, frequency, and duration of heavy precipitation and flooding events, which may raise the risk of diarrheal diseases
and vector- borne infections.
The 1993 outbreak of hantavirus pulmonary syndrome (an acute respiratory disease) in the Southwestern United States provides a dramatic example of how severe weather events can promote disease transmission.
A number of diseases—such as malaria, dengue fever, and viral encephalitis
infections—are highly sensitive to changes in the environment. The 1993 outbreak of hantavirus pulmonary syndrome
(an acute respiratory disease) in the Southwestern United States provides a dramatic example of how severe weather events can promote disease transmission. The outbreak was traced to a steep increase in the population of deer mice that carry the virus—an increase caused by heavy rains after 6 years of drought, which led to an abundance of food sources for the deer mice. West Nile virus
emerged in the Eastern United States in 1999, during the hottest and driest summer in a century. Subsequent outbreaks in the Midwest in 2003, 2005, and 2006 also coincided with heat waves. Scientists believe that hot weather may speed up both the breeding cycle of mosquitoes and replication
of the virus in insects’ guts.
Several recent studies have examined the relationship between the occurrence of infectious diseases and short-term climate variation, in particular the influence of the El Niño-Southern Oscillation (ENSO) cycle on the transmission of vector-borne and nonvector-borne infections such as malaria, dengue fever, and cholera
. ENSO is the irregular cycling of surface water temperatures between warm and cool phases across parts of the Pacific Ocean. Global climate change is expected to intensify ENSO-related climate variability.
Scientists are currently debating the future effects of climate change on vector-borne disease. Some experts predict that many vector-borne diseases will expand their range to higher elevations and latitudes in response to global warming; others claim that human impacts on the local ecology, such as deforestation and water use and storage, have a far stronger influence on the frequency and range of vector-borne infections.
A secondary effect of climate change also promotes infectious disease. Human migration often follows extreme weather or weather-associated events, including hurricanes, cyclones, fires, drought, and floods. The risk of disease outbreaks increases after such disasters due to population displacement, resulting in unsafe food and water, crowding, and poor access to health care.
Learn more about these related topics: