How does climate change affect disease?
Climate change and human health are interconnected in many complex ways. The impacts of climate change include warming temperatures, changes in precipitation, an increase in the frequency or intensity of some extreme weather events, changes in the distribution of wildlife, and rising sea levels. These impacts threaten our health by affecting the food we eat, the water we drink, the air we breathe, and the weather we experience.
Climate change may especially affect people who live in areas that are vulnerable to coastal storms, drought and sea-level rise, or people who live in poverty, older adults, and immigrant communities. People in developing countries may be the most vulnerable to health risks globally, but climate change poses significant health threats even in wealthy nations.
Climate change scenarios include a change in the distribution of infectious diseases with warming and changes in outbreaks associated with weather extremes. The ranges of several vector-borne diseases are already changing in altitude due to warming. The incidence of mosquito-borne parasitic and viral diseases is among those diseases most sensitive to climate (e.g. West Nile Virus, malaria, Dengue fever, etc.). Climate change affects disease transmission by shifting the vectors’ geographic range and by shortening the pathogens’ incubation period. The temperature may modify the growth of disease-carrying vectors by altering their biting rates, as well as affecting vector population dynamics and altering the rate at which they come into contact with humans. A shift in temperature regime can alter the length of the transmission season. Disease-carrying vectors may adapt to changes in temperature by changing geographical distribution.
Possibly one of the most dangerous consequences of climate change is the potential for the emergence or re-emergence of novel pathogenic bacteria, viruses, and parasites. Heat stress may elevate the potential for animal-to-animal transmission of zoonotic pathogens. Moreover, it may provide possibilities for pathogens to cross between species. For many pathogens, the environment plays an important role in the transmission, and hence changing environmental conditions (e.g. temperature) may alter the geographical distribution, diversity, levels, and seasonality of the pathogen in nature, which could lead to emerging outbreaks (e.g. Ebola, SARS, MERS, west Nile Fever).
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