Pathogenic diseases that impact humans are being exacerbated by climate change, according to a paper published in Nature Climate Change on Aug. 15.

Of the 375 infectious diseases studied, greenhouse gas emission heightened the negative impacts of 58% (218) of the diseases.

While the impact of 16% of diseases was diminished by changes in the climate, researchers “also found that most diseases that were diminished by at least one hazard were at times aggravated by another and sometimes even the same hazard.”

Prior studies on such connections have focused on one of three key aspects of climate impacts (specific pathogens, hazards or transmission types).

By contrast, the research documented in this paper sought to integrate available data to obtain a better sense of the degree to which climate change is affecting the transmission of disease, focusing specifically on the impact of GHG emissions.

A key factor resulting from climate change and contributing to the heightened impacts of disease is the expansion of the geographical range of species (mosquitos, ticks, fleas, birds, mammals, etc.) that carry pathogens impacting humans.

In addition, warmer temperatures at higher elevations have allowed water-borne pathogens to survive the winter months and then be carried downstream to lower elevations. Pathogens from the past that have been trapped in ice, and for which humans no longer carry immunity, could emerge with the increased melting of the polar ice caps.

Changes in the human body resulting from climate change has also played a role in the spread of pathogens. For example, the inability of the body to adjust to significant temperature changes has been associated with influenza outbreaks, while “stress and cortisol variations [are] a likely mechanism by which climatic hazards reduce the body’s capacity to deal with pathogens.”

Climate impacts often provide a more hospitable environment for certain pathogens, making it easier for them to reproduce and spread, causing them to be more virulent, and extending the time periods in which humans are most likely to be exposed to certain pathogens.

“The sheer number of pathogenic diseases and transmission pathways aggravated by climatic hazards reveals the magnitude of the human health threat posed by climate change and the urgent need for aggressive actions to mitigate GHG emissions,” the researchers concluded.

The full paper is available here. An interactive page showing the connection between climatic hazards and pathogenic diseases studied for the paper is available here.

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