Climate change can influence spread of disease in many ways
- As temperatures rise, mosquito season may become longer and spread to places that are currently relatively cold. The reproduction of bacteria like Salmonella also increases as temperature rises.
- Flooding can increase the risk of gastroenteritis and diseases transmitted by rodents. Increased rainfall, flooding and humidity also creates more viable conditions for breeding of mosquitoes and other vectors.
- Low rainfall in many places can lead to water scarcity, which may reduce hygiene practices thus leading to gastrointestinal illnesses.
- Climate change can bring pressure on agricultural productivity, causing issues such as crop failure, malnutrition, starvation, increased population displacement, and resource conflict. These pressures can increase human susceptibility to infectious diseases.
Some projections of disease due to climate change
- If global temperatures increase by 2 to 3°C, the population at risk for malaria is expected to increase by 3-7%. One example seen so far is the spread of malaria into highland regions of East Africa, where this disease previously did not exist.
- By 2030 there is expected to be 10% more diarrhoea than there would have been with no climate change.
- Projected geographic distributions of West Nile virus in North America show an expansion under future climate for 2050 and 2080.
- “More Mosquito Days Increasing Zika Risk in U.S.” (Climatecentral.org, 2016) found that since 1980, most major cities in the United States have seen an overall increase in days conducive for Asian Tiger Mosquitoes (Aedes albopictus), which is one of the species known to transmit the Zika virus.
Here are some of the diseases that can spread due to climate change - Malaria, Lyme disease, Yellow fever, Dengue fever, Zika virus, Chikungunya, West Nile virus, Cholera, Salmonellosis (Salmonella infection), Plague, Typhoid , African trypanosomiasis (sleeping sickness), Tick-borne encephalitis, Ross River fever, Arbovirus, Giardiasis (beaver fever)
See here for key studies that assess the relationship between extreme weather events and infectious diseases.
Wu X and others, “Impact of Climate Change on Human Infectious Diseases: Empirical Evidence and Human Adaptation” (2016) 86 Environment International 14
Shuman EK, “Global Climate Change and Infectious Diseases” (2010) 362 New England Journal of Medicine 1061
Burkholder B, “Climate Risk and Spread of Vector-Borne Diseases” (Climate Nexus, 2017)
Jordan R, “How Does Climate Change Affect Disease?” (Stanford Earth, 2019)
Derouin S, “What a Warming Planet Means for Mosquito-Borne Diseases” (Stanford Earth, 2017)
Harrigan RJ and others, “A Continental Risk Assessment of West Nile Virus under Climate Change” (2014) 20 Global Change Biology 2417
Lloyd S, Kovats R and Armstrong B, “Global Diarrhoea Morbidity, Weather and Climate” (2007) 34 Climate Research 119
Chretien J-P and others, “Global Climate Anomalies and Potential Infectious Disease Risks: 2014-2015”  PLoS Currents
“More Mosquito Days Increasing Zika Risk in U.S.” (Climatecentral.org, 2016)