Research shows that climate risks could exacerbate more than half of known infectious diseases in humans

A recent article published in the magazine Nature Climate Change demonstrated that climate change can exacerbate approximately 50% of recognized human pathogenic diseases.

Study: More than half of known human pathogenic diseases may be exacerbated by climate change. Image Credit: Sepp Photography

Background

Continued emissions of greenhouse gases (GHGs) are increasing various climatic risks, which in turn exacerbate human pathogenic diseases. The pandemic of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), amply demonstrating the social unrest caused by infectious diseases, offers alarming clues to the potential impacts of impending health crises caused by climate change.

While it is well known that climate change affects pathogenic diseases, the degree of human susceptibility to pathogenic diseases affected by climate change is not fully known. With few outliers, previous research on the relationship between climatic hazards and human pathogenic diseases has typically focused on particular classes of pathogens (such as bacteria or viruses), climatic hazards (such as warming, precipitation, or flooding), or modes of transmission (such as vector, food -, water-based). Therefore, as it relates to pathogenic diseases, measuring the full threat to humans posed by climate change is hampered by the inability to combine available information.

About the study

In the current study, the researchers methodically searched for empirical evidence of the effects of 10 climate changes sensitive to GHG emissions on each recognized human pathogenic disease. The 10 GHG-sensitive climatic hazards analyzed in the study were drought, warming, wildfires, heat waves, flooding, precipitation, sea level rise, storms, land cover change and ocean climate change.

The team conducted three interdependent literature reviews to identify case reports of pathogenic diseases affected by climate hazards. On the first search, they conducted separate studies for each combination of the term “disease” with each of the 10 climate hazards identified as sensitive to GHG emissions. In the second search, the researchers conducted separate searches for scientific papers, combining each disease name from two reliable databases of infectious diseases with each of 10 climatic hazards.

The authors then conducted additional searches for combinations of disease and climatic risk, with the previous two searches yielding no case studies. They first generated a table with all the diseases identified by searches 1 and 2 as rows and each climate risk as columns. In addition, in the third search, the team used alternative names for the pathogens and diseases. In addition, they used Google Scholar for all the questions.

Results

The authors found 3,213 empirical cases in which climate risks were linked to pathogenic diseases. These case examples were linked to 286 different pathogenic diseases, 277 of which had at least one climate risk that made them worse. While some climatic risks reduced 63 diseases, 54 of them were occasionally exacerbated by other climatic risks. Indeed, climate risks uniquely reduced only nine pathogenic diseases.

The scientists documented diseases that exacerbate climatic hazards. The collection of pathogenic diseases that exacerbate climatic hazards is responsible for 58% of all infectious diseases found to have affected humanity worldwide. In detail, climatic hazards exacerbate 218 of a reliable list of 375 pathogenic diseases known to have affected humans.

The team identified 1,006 different pathways through which climatic hazards, through different modes of transmission, have led to the emergence of pathogenic diseases. They noted that 76, 69, 45, 24, 23, 12 and nine diseases caused by viruses, bacteria, animals, fungi, protozoa, plants and chromists, respectively, were affected by warming, precipitation, flooding, drought, storms, land cover change, ocean climate change, fires, heat waves and sea level rise associated with 160, 122, 121, 81, 71, 61, 43, 21, 20 and 10 unique diseases, respectively.

Vectors mainly spread pathogenic diseases, namely 103 different diseases. However, the researchers also found 78, 60, 56 and 50 unique disease examples for the water, air, direct contact and food transmission channels, respectively. There were 19 common disease names (such as gastrointestinal infections) with no causative pathogen data among all case examples of pathogenic diseases adversely affected by climate hazards. In addition, there were no details on the transmission mechanism for 116 diseases.

conclusions

Overall, in the current study, the team found that climatic hazards exacerbate 58% (i.e. 218 out of 375) of the infectious diseases that people worldwide experience at any given time. On the other hand, it occasionally reduced 16% of pathogenic diseases. Empirical cases showed 1006 different ways in which climatic risks led to pathogenic diseases through different transmission methods.

In particular, climate risks exacerbate many human pathogenic diseases and modes of transmission, exceeding the capacity of societal adaptation, underscoring the urgent need to address the root of the problem, which is to reduce greenhouse gas emissions.

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