Kayla Knilans received her Ph.D. from the University of North Carolina and currently studies inflammatory mediators and epithelial repair in inflammatory bowel disease.
Climate change discussions frequently focus on the geological and ecological effects of climate change, such as rising sea levels and changing or extreme weather patterns. A less frequently explored aspect of climate change in the media is its impact on infectious diseases. But this is a critical issue for consideration in climate change discussions, as climate and infectious diseases are strongly linked. Temperature, humidity, rainfall, and even sunlight exposure and wind can have an impact on communicable illnesses. These effects can be directly on the pathogen, on their vectors or hosts, or on their living environment. Weather, then, can impact both the timing and the severity of disease outbreaks. In this context, climate change is not only an issue of environmental preservation, but one that is also tightly linked to public health.
Based on historical data from El Niño, La Niña, droughts, floods, and major weather events such as hurricanes, scientists have built models to predict the infectious diseases most likely to become greater threats to public health as a consequence of climate change. Predicting the impact of climate change on some diseases can be difficult due to confounding interactions with the climate. For example, while influenza viral particles are most stable at low humidity (20%–40%), viral stability is minimal at intermediate humidity (50%), and then rises again at high at elevated humidity (60%–80%), before falling sharply at very high humidity ( > 80%). In other cases, there is more consensus on the impact of climate change on infectious diseases, such as with vector borne diseases.
Vector-borne diseases that are transmitted by mosquitos are of particular concern, as the habitable environment for two critical species of mosquitos, Aedes aegypti and Aedes albopictus, has been expanding. Consequently, mosquito-borne infections have been on the rise. The global distribution of malaria, for example, is expected to increase as a consequence of warmer global temperatures. One area of particular concern and significant study are the highland regions of Africa where malaria is currently not endemic, but has historically seen increases in disease in warmer years. Dengue virus is also expected to expand its global distribution, with both the United States and Japan having reported local infections after nearly a century of absence from those countries. In addition, the 2015 Zika virus outbreak that has become a major ongoing public health issue was found to be fueled by the combination of El Niño that year and overall warming temperatures.
Social and economic factors also play a significant role in assessing the risk for infectious diseases as it pertains to climate change. These factors include access to clean water, a public health system with good infrastructure and an ability to respond to outbreaks, the presence of biosurveillance programs to identify outbreaks, and accurate early-warning systems for major weather events. Organizations such as the United Nations Environment Programme, the World Health Organization, and the Intergovernmental Panel on Climate Change, seek to provide countries with specific policy recommendations to mitigate disease outbreaks. Organizations like the Collaborative Adaptation Research Initiative in Africa and Asia seek to identify regions most vulnerable to the effects of climate change and support research and policy initiatives in those regions. The University of Notre Dame’s Global Adaptation Index has found that while many such countries are still vulnerable and have a low readiness to respond to climate change, they are making significant strides in reducing their susceptibility. Kenya, Bangladesh, and Burkina Faso, for example, have all prepared action plans and established financing for combating climate change. These countries in particular will need robust scientific research to inform the link between climate change and infectious disease to ensure good policy decisions and the proper allocation of resources.
A recent review article identified a critical lack of collaboration between scientific groups attempting to predict the epidemiological impact of climate change on infection risk and basic science researchers that work to understand the direct impact of climate variables on pathogens. Moving forward, scientific collaborations will be critical for predicting the changing patterns of infectious diseases so that countries can be well informed of the resources that will be needed to combat and prevent future outbreaks. It is also essential that countries are willing to enact policies that will both slow the progression of climate change and allocate resources for outbreak containment and prevention, including resources for less developed nations.