Man-made climate change clearly favors the spread and outbreak of infectious diseases. That’s what a study by the University of Hawaii published on Monday (8) in the scientific journal Nature Climate Change points out.
“It was really scary to see that greenhouse gas emissions are such a huge threat to health,” says Camilo Mora, a professor at the University of Hawaii’s College of Social Sciences and lead author of the study.
By evaluating more than 800 scientific articles, the researchers found that 58% of the infectious diseases analyzed were exacerbated by climate change. And a connection could be proven in over 3,000 individual cases.
According to the study, of the 375 diseases analyzed, 160 can be aggravated by heat, 121 by floods, 71 by storms, 81 by drought and 43 by ocean warming.
“Given the far-reaching and widespread consequences of the Covid-19 pandemic, it was truly frightening to discover the enormous health vulnerability resulting from greenhouse gas emissions,” adds Mora.
Droughts, storms and heat waves
The links between climate change and disease can be varied: water and food shortages caused by droughts can, for example, drive wild animals closer to residential areas, increasing the risk of individuals contracting a disease transmitted by animals or parasites.
Droughts can also end up forcing people to consume contaminated water, which can cause illnesses such as diarrhea or cholera.
In turn, storms, heavy rains and flooding can damage roads, power lines and sewer systems, as well as interrupt drinking water supplies. Such events have already led to outbreaks of hepatitis A and E, rotavirus and typhoid fever.
Another point is that the immune system may be weakened, for example, due to malnutrition caused by drought or heat waves, leaving you more susceptible to disease. Stress from other weather extremes can also weaken the immune systems of both humans and animals.
The researchers found, for example, that heat and lack of food in bats led to increased virus spread and promoted outbreaks of the Hendra virus — which can cause severe encephalitis in humans.
In total, scientists have identified more than a thousand different ways in which climate change could promote disease outbreaks.
Mosquitoes adapted to Europe
Higher temperatures can not only promote the spread of pathogens and increase the risk of infection, but also favor the spread of carriers, so-called vectors. These could be mosquitoes or ticks, for example, which breed easily in warmer areas. Due to rising temperatures, they are now able to live in regions where they were not native before.
The study found more than 100 vector-borne diseases that are intensifying with climate change.
“We have already observed in Germany and Europe the influence of events related to climate change on pathogens”, says Renke Lühken, from the Bernhard Nocht Institute for Tropical Medicine (BNITM), in Hamburg, in an interview with DW. The virologist specializes in insect-borne diseases and was not involved in the study.
According to Lühken, experts are particularly concerned about the spread of the Asian tiger mosquito (Aedes albopictus). It is currently establishing itself in much of Europe and “is particularly responsible for outbreaks of chikungunya virus and dengue in the Mediterranean region”, adds the virologist.
“It is very aggressive and assertive: it is capable of transmitting more than 20 different viruses in humans and displacing native species of mosquitoes. It is also very adaptable when it comes to choosing suitable breeding sites”, explains Artur Jöst, biologist and specialist in mosquitoes. at the Institute of Dipterology in Speyer, Germany.
Aggressive approach is required
The Zika virus and dengue cause high fever, rashes and severe headaches, in the bones and in the body. In a 2020 study, researchers at the University of Georgia in the United States warned that by 2050, more than 1.3 billion people will live in areas where Zika can spread. More than 700 million will live in temperatures that make year-round transmission possible.
“This is worrisome, because there are only approved vaccines for some of these pathogens,” says BNITM’s Lühken.
Vectors transmit 17% of all infectious diseases. Nearly 700 million people contract mosquito-borne diseases every year, and more than 1 million die.
According to the authors of the Nature Climate Change paper, it is difficult or even impossible to prevent — or adapt to — the increased spread of disease due to climate change, as pathogens and transmission routes are numerous.
For experts, therefore, what is needed is an “aggressive approach” in order to reduce greenhouse gas emissions.
