Climate hazards such as floods, heat waves, and drought have worsened more than half of the hundreds of known infectious diseases in people, including malaria, hantavirus, cholera, and even anthrax.
The researchers reviewed the medical literature of established cases of illness and found that 218 of the 375 known human infectious diseases — 58 percent — appeared to be made worse by one of 10 types of extreme weather linked to climate change. according to a study published Monday in the journal Nature Climate Change.
Physicians dating back to Hippocrates have long linked disease to the weather, but this study shows just how pervasive the influence of weather is on human health.
In addition to looking at infectious diseases, the researchers broadened their search to look at all kinds of human diseases, including non-infectious diseases like asthma, allergies, and even animal bites to see how many diseases could be linked to climate hazards in some way. including infectious diseases. They found a total of 286 unique illnesses and of those 223 of those seemed to be made worse by weather hazards, nine were lessened by weather hazards and 54 had both aggravated and minimized cases, the study found.
The new study doesn’t do the math to attribute changes, probabilities or magnitude of specific diseases to climate change, but finds cases where extreme weather was one likely factor among many. The study mapped the 1,006 connections between climate hazard and disease.
“If the climate is changing, the risk of these diseases is also changing,” said study co-author Dr. Jonathan Patz, director of the Institute for Global Health at the University of Wisconsin-Madison.
Doctors, like Patz, said they should think of illness as symptoms of a sick Earth.
“The findings of this study are frightening and well illustrate the enormous consequences of climate change on human pathogens,” said Dr. Carlos del Rio, an infectious disease specialist at Emory University, who was not part of the study. “Those of us in infectious disease and microbiology must make climate change one of our priorities and we must all work together to prevent what will undoubtedly be a catastrophe as a result of climate change.”
The study’s lead author, Camilo Mora, a climate data analyst at the University of Hawaii, said what’s important to note is that the study isn’t trying to predict future cases.
“There is no speculation here,” Mora said. “These are things that have already happened.”
An example that Mora knows first-hand. About five years ago, Mora’s house in rural Colombia was flooded (for the first time in his memory there was water in his living room) and Mora contracted Chikungunya, a nasty virus spread by mosquito bites. . And although he survived, he still feels pain in his joints years later.
Sometimes climate change acts in strange ways. Mora includes the 2016 case in Siberia when a decades-old reindeer carcass, killed by anthrax, was unearthed when permafrost thawed from warming. A boy touched it, gave him anthrax and started an outbreak.
Mora originally wanted to look at medical cases to see how COVID-19 intersected with climate hazards, if at all. He found cases where extreme weather exacerbated and decreased the chances of COVID. In some cases, extreme heat in poor areas caused people to congregate to cool off and expose themselves to illness, but in other situations, heavy downpours reduced the spread of COVID because people stayed home and indoors, away from the disease. of others.
Kristie Ebi, a longtime climate and public health expert at the University of Washington, cautioned that she had concerns about how the conclusions were drawn and some of the study’s methods. It is an established fact that the burning of coal, oil and natural gas caused more frequent and intense extreme weather conditions, and research has shown that weather patterns are associated with many health problems, she said.
“However, correlation is not causation,” Ebi said in an email. “The authors did not discuss the extent to which the reviewed climate hazards changed over the study time period and the extent to which the changes have been attributed to climate change.”
But Dr. Aaron Bernstein, acting director of the Center for Climate, Health, and the Global Environment at the Harvard School of Public Health, Emory’s del Rio, and three other outside experts said the study is a good warning about climate change. and health for now and the future. Especially when global warming and habitat loss bring animals and their diseases closer to humans, Bernstein said.
“This study underscores how climate change can load the dice in favor of unwelcome infectious surprises,” Bernstein said in an email. “But of course, just reporting what we already know and what is not yet known about pathogens can be even more convincing about how preventing further climate change can prevent future disasters like COVID-19.”
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