More Than Half Of Human Pathogenic Diseases May Be Exacerbated By Climate Change

More than half of the known human pathogens such as dengue fever, hepatitis, pneumonia, malaria, Zika and others, may be exacerbated by climate change. This striking and impressive finding is the subject of a research paper published on August 8 Nature Climate Change by a team of researchers from the University of Hawaii at Mānoa. The researchers conducted a systematic search for empirical examples of the effects of 10 greenhouse gas (GHG)-sensitive climate hazards on every known human pathogen. These risks included warming, drought, heat waves, wildfires, extreme rainfall, floods, storms, sea level rise, ocean biogeochemical change and land cover change. Combining two authoritative lists of all known infections and pathogenic diseases that have affected humanity in recorded history, the researchers then examined over 70,000 scientific papers for empirical examples of every possible combination of climate hazards affecting each of the known diseases. The research revealed that warming, rainfall, floods, drought, storm surge, land cover change, ocean climate change, wildfires, heat waves and sea level changes were all found to affect disease caused by viruses, bacteria, animals, fungi, protozoa, plants and chromists. Pathogenic diseases were primarily vector-borne, although case examples were found for transmission routes including waterborne, airborne, direct contact, and food. Ultimately, the research found that over 58%, or 218 out of 375, of known human pathogenic diseases had at some point been affected by at least one climate hazard through 1,006 unique pathways. “Given the widespread and pervasive consequences of the COVID 19 pandemic, it was truly frightening to discover the massive health vulnerability resulting from greenhouse gas emissions,” said Camilo Mora, professor of geography in the College of Social Sciences (CSS) and lead . author of the study. “There are too many diseases and transmission routes to think we can really adapt to climate change. It highlights the urgent need to reduce greenhouse gas emissions worldwide.” An interactive website showing each link between a climate hazard and a case of disease was developed by the research team. The tool allows users to query specific risks, pathways and disease groups and view available data. The UH Mānoa research team included experts from CSS, the Department of Earth Sciences in the School of Ocean and Earth Science and Technology (SOEST), the Graduate Program in Marine Biology in the School of Life Sciences, the Department of Natural Resources and Environmental Management in the College of Tropical Agriculture and Human Potential (CTAHR) and Hawaii Institute of Marine Biology at SOEST. Key findings include:

Climate risks bring pathogens closer to humans. Numerous climatic hazards increase the area and duration of environmental suitability facilitating the expansion of vectors and pathogens. Changes in warming and precipitation, for example, have been associated with the expansion of the range of vectors such as mosquitoes, ticks, fleas, birds, and many mammals involved in outbreaks of viruses, bacteria, animals, and protozoa such as dengue , chikungunya, plague, Lyme disease, West Nile virus, Zika, trypanosomiasis, echinococcus and malaria. Climate risks bring people closer to pathogens. Climatic hazards were implicated in the forced movement and migration of people, causing or increasing new contacts with pathogenic organisms. Storms, floods and rising sea levels, for example, have caused displacements of people involved in cases of leptospirosis, cryptosporidiosis, Lassa fever, giardiasis, gastroenteritis, legionnaires’ disease, cholera, salmonellosis, shigellosis, pneumonia, typhoid diseases, hepatitis . Climatic hazards have enhanced specific aspects of pathogens, including improved climatic suitability for reproduction, accelerated life cycle, increased seasons/duration of potential exposure, enhanced pathogen-vector interactions (e.g. by reducing incubations ) and increased virulence. Warming, for example, had positive effects on mosquito population growth, survival, biting rates and virus reproduction, increasing the transmission efficiency of West Nile virus. Climatic hazards have also reduced the human ability to cope with pathogens, changing the body’s condition. added stress from exposure to hazardous conditions. forcing people into unsafe conditions; and destroying infrastructure, forcing exposure to pathogens and/or reducing access to medical care. For example, drought favored poor sanitation responsible for cases of trachoma, chlamydia, cholera, conjunctivitis, cryptosporidium, diarrheal diseases, dysentery, Escherichia coli, Giardia, salmonella, scabies, and typhoid fever.

The researchers also found that while the vast majority of diseases were made worse by climate hazards, some were reduced (63 of 286 diseases). Warming, for example, appears to have reduced the spread of viral diseases possibly related to conditions unsuitable for the virus or due to stronger immune systems in warmer conditions. However, most diseases that were reduced by at least one risk were occasionally exacerbated by another and sometimes even by the same risk. “We knew that climate change could affect human pathogens,” said co-author Kira Webster, Ph.D. school student. “However, as our database grew, we were both fascinated and distressed by the overwhelming number of case studies available that already show how vulnerable we are becoming to continued rising greenhouse gas emissions.” Greenhouse gases are causing more change than we can handle More information: Camilo Mora, More than half of known human pathogenic diseases may be exacerbated by climate change, Nature Climate Change (2022). DOI: 10.1038/s41558-022-01426-1. www.nature.com/articles/s41558-022-01426-1 Provided by the University of Hawaii at Mānoa Reference: More than half of human pathogens may be exacerbated by climate change (2022, August 8) Retrieved August 8, 2022, from
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