Climate Change and the Spread of Infectious Diseases

Global temperature rise, warming oceans, shrinking ice, decreased snow cover, ocean acidification and rise in sea levels. Do these terms sound familiar? These terms are indeed stark reminders of how human beings continue to damage the planet.

Climate change is one of the most severe threats to human health and well-being. While the scientific community has made tremendous progress in eradicating many diseases, not a lot of research has been put towards the perplexing topic of climate change and the spread of infectious diseases. Long before the role of infectious agents was discovered, humans knew that climatic conditions affect epidemic diseases. Roman aristocrats spent their summers in hill resorts to avoid Malaria. South Asians preferred curried foods in summers to avoid diarrhea.

Climate change refers to long-term shifts in weather conditions and patterns of extreme weather events. Appropriate climate and weather conditions are necessary for the survival, reproduction, distribution and transmission of disease pathogens. Thus, long-term climate change and weather shifts tend to favor the spread of several infectious diseases and extreme weather conditions might create opportunities for newer outbreaks or outbreaks at non-traditional places.

It has been known for a while now that warming temperatures can help certain diseases. Malaria, which kills an estimated 650,000 people a year, thrives in the hot and humid areas where the Anopheles mosquito can live. The link between malaria and extreme climatic events has long been studied in India, for example. Early last century, the river-irrigated Punjab region experienced periodic malaria epidemics. Excessive monsoon rainfall and high humidity was identified as a major influence, enhancing mosquito breeding and survival. As the climate warms, it is expected that the territory where the mosquito and the malaria parasite will be able to live will likely expand, putting more people at risk. Another mosquito borne tropical illness, the Dengue fever was re-established in Florida keys although it was wiped out decades ago. Such diseases will emerge at a larger scale in a warmer world. If global temperatures increase by 2 to 3°C, as predicted, it is estimated that the population at risk for malaria will increase by 3 to 5%, which means that millions of additional people will be at risk of malaria each year.

Not only airborne diseases but waterborne infectious diseases are also strongly affected by climate. During times of drought, water scarcity results in poor sanitation, thus exposing the population to potentially contaminated water. For example, an epidemic of cholera in northern Kenya happened in the wake of a severe drought.

Sunshine is another important climate variable that may affect the pathogens of infectious diseases. For example, sunshine hours and temperature act synergistically during cholera periods to create a favorable condition for the multiplication of Vibrio cholerae in aquatic environments.

These various climatic pressures can affect the distribution and emergence of various infectious diseases. A call for more research seems an obvious suggestion but also robust surveillance and enforcement of the International Health Regulations are absolutely essential to win the war against pathogens.

We can play a significant and active role by adopting measures to control and alleviate the negative health impacts of climate change. We need to constantly improve public health programs and allocate financial resources based on our predicted health risks from climate change. Medical teaching facilities and researchers can contribute to this process as being efficient as reporting medical cases so that scientists are able to map out this changing process through time and across space. Medical Schools curriculum can be help meet the need of developing early warning systems, protocols for information sharing, public health awareness campaigns.


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Mitali Adlakha

Is a contributor to The Almost Doctor’s Channel.