Study: World faces health crisis due to climate change

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Scientists are alarmed: more than half of infectious diseases are aggravated by extreme weather such as heat or floods. The immune system is weakened, diseases spread faster.

Man-made climate change is clearly promoting the spread and outbreak of infectious diseases. This is the conclusion of the authors of a University of Hawaii study published in the scientific journal Nature.

“It was really frightening to see that greenhouse gas emissions are such a massive health threat,” said Camillo Mora, professor in the College for Social Science at the University of Hawaii and lead author of the study.

In the evaluation of over 800 scientific papers, the researchers found that 58 percent of the infectious diseases examined are aggravated by climate change. A connection could be proven in over 3000 individual cases. Of the 375 diseases examined, 160 can be aggravated by heat, 121 by floods, 71 by storms, 81 by droughts and 43 by the warming of the oceans.

“The societal upheavals of the COVID-19 pandemic provide a disturbing insight into an emerging health crisis fueled by climate change,” the study states.

Dirty water from drought or storms

The connections between climate change and diseases are very different: water and food shortages caused by droughts can, for example, lead to wild animals venturing closer to residential areas. This increases the risk for humans of catching a disease transmitted by animals or parasites.

Full hospitals. New cases of cholera only appeared in Cameroon in April.

Droughts also mean that people may be forced to drink polluted water. This can lead to diarrheal diseases or cholera.

Storms, heavy rain and flooding can damage roads, power lines or the sewage system and cut off the supply of clean drinking water. Such events have already led to outbreaks of hepatitis A and E, rotavirus and typhoid in previous cases.

Drought, storms and flooding can make access to clean water impossible

Another point: The immune system is weakened by malnutrition caused by drought or heat waves and is therefore also more susceptible to diseases. Stress from other weather extremes can also weaken the immune system of humans and animals.

For example, the researchers found that heat and lack of food in bats led to increased shedding of viruses and promoted Hendravirus outbreaks. The Hendra virus can cause severe encephalitis in humans.

In total, the scientists identified over 1000 different ways in which climate change could promote the outbreak of diseases.

Exotic vectors already in Europe

Higher temperatures can not only increase the spread of pathogens or the risk of infection, they also promote the spread of the carriers, the so-called “vectors”. This can be, for example, mosquitoes or ticks, which breed well in warm areas. Due to global warming, they can now live in regions where they were not previously native.

The study found more than 100 vector-borne diseases that are being exacerbated by climate change. 

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“In Germany and Europe we are already observing the influence of climate change-related events on pathogens,” says Dr. Renke Lühken from the Bernhard Nocht Institute for Tropical Medicine (BNITM) in Hamburg told DW. The virologist is an expert on insect-borne diseases and was not involved in the study.

700 million people contract a mosquito-borne disease each year

The experts are particularly concerned about the spread of the Asian tiger mosquito, according to Lühken. It is currently establishing itself in large parts of Europe and “is particularly responsible for outbreaks of the chikungunya virus and dengue virus in the Mediterranean region,” the virologist continues.< /p>

“It is very aggressive and assertive. It is capable of transmitting more than 20 different viruses to humans and displacing native mosquito species. It is also very adaptable when it comes to choosing suitable breeding sites,” adds Artur Jöst, biologist and Expert on Asian tiger mosquitoes at the Institute for Dipterology in Speyer.

Zika virus and dengue fever lead to high fever, skin rash and severe headache, bone and body pain. In a 2020 study, researchers at the University of Georgia, USA, warn that by 2050 more than 1.3 billion people will live in areas where the Zika virus can spread. More than 700 million will live with temperatures that make transmission possible all year round.

“This is worrying because only a few of these pathogens have approved vaccines,” says Lühken from the BNITM.< /p>

17 percent of all infectious diseases are transmitted by vectors. Nearly 700 million people contract a mosquito-borne disease every year, and more than a million die.

“Aggressive crackdown” against…

At the beginning of the week, the President of the Robert Koch Institute (RKI), Lothar Wieler, called for more attention to be paid to exotic diseases in Germany. 

Germany is also suffering from drought. The Rhine is extremely low this year, ships can only sail to a limited extent.

“Climate change in Germany is leading to an expansion of the habitats for mosquitoes and ticks,” Wieler explained to journalists.

“Many mosquito and tick species can transmit viral, bacterial and parasitic pathogens,” says Wieler. 'Malaria may also return.'

According to the Nature study researchers, preventing or adapting to the increased spread of disease caused by climate change is difficult or even impossible. The pathogens and transmission routes are too numerous for that. From their point of view, an “aggressive approach” to reducing greenhouse gas emissions is therefore necessary.