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Photo credit, AGENCE PHOTO HUW EVANS
Drought is an effect of climate change which has had an impact on certain diseases.
There is growing evidence that climate change is altering our lives.
But today, a team from the University of Hawaii (USA) published a study claiming that climate change has influenced more than 200 diseases.
The study, published last August in the scientific journal Nature, initially aimed to determine whether climate change had influenced the emergence and spread of covid-19, but it was expanded and cross-checked with data from more than 70,000 scientific articles and its incidence in more than 200 diseases.
Camilo Mora, a Colombian associate professor in the Department of Geography and Environment at the University of Hawaii, led this study of how up to 200 diseases have been affected by climate change.
“Climate change has complicated 58% of all of humanity’s diseases,” Mora says.
“A lot of diseases that are already there, but it can make them worse.
He explains with an example: “I can feel strong, but suddenly Mike Tyson comes. I can defend myself, but he will hit me. But if three others like him get on the same stage, I will not survive.
“The vulnerability we have to this is strong,” he adds.
In this research, the authors claim to have found 3,213 empirical examples in which climate risks were implicated in pathogenic diseases.
Among the main phenomena caused by climate change, they identified four as affecting the most diseases: global warming, which is implicated in 160 different diseases, increased rainfall (in 122), floods (121 ) and drought (81).
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Floods put us in contact with a variety of disease-causing pathogens.
They found more than 1,000 unique pathways in which “climatic hazards, through different types of transmission, resulted in pathogenic disease occurrences,” but grouped them into four general processes that relate to the behavior of the pathogen (what infects us in one way or another) and the one who is infected, i.e. people.
1. Pathogens that approach humans
This is the geographic shift of species due to climate change. It alters the area they normally live in due to something that is related to climate change, such as increased rainfall, drought, or melting snowpack, and because of that animals and all pathogens they bring with them, move. For example, explains Mora, the bats that are found in the middle of the forest and live there with their pathogens. “Following, for example, a fire, the bat has to move, it gets closer to us, and with it, all its pathogens. “Their habitat is affected, we throw the ranch to the animals”, he says. And this increases the likelihood of contact between the two and, therefore, the spread of any disease.
2. Human approach to pathogens
With climate change, meteorological phenomena have increased, which has led to the displacement of human beings, temporarily or permanently, to places where the pathogens causing various diseases are concentrated.
The increase in the number of hurricanes, or floods, is a good example. “You have to walk around (in water, in the middle of a flood) and it’s full of bacteria and viruses. You get into the pathogen,” Mora says.
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The increase in rainfall has led to an increase in the number of mosquitoes and therefore mosquito-related diseases.
This increases contact between humans and pathogens and therefore the likelihood of associated diseases.
The drought has also prompted people to move.
“For example, in Africa, people have to migrate where there is water. In their movement, they carry animals and with them their pathogens, and they all congregate where there is water.
And, once more, it increases the likelihood of getting sick from increased contact with pathogens.
3. Climate change makes some diseases worse
When climatic conditions change in certain places, organisms and pathogens die or adapt. By natural selection, the fittest survive. And this has an impact on diseases.
For example, Mora explains, we have fever as a mechanism for fighting certain diseases and “it generates conditions that the pathogens do not like”.
But due to heat waves, pathogens tolerate higher temperatures.
“If there is a heat wave of 40 or 42 degrees Celsius, it kills some pathogens, but those who survive have the ability to withstand that, which is a higher temperature than a normal human fever. The agent pathogen therefore already has the ability to counter your natural defences,” he explains.
This same increase in temperature leads to an acceleration of the reproductive cycle in some species.
It is also linked to the increase in the rainy season in some regions and, in its case, to mosquitoes, important vectors of diseases such as chikungunya, yellow fever and dengue fever.
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With increasing drought, animals and people tend to congregate in places where there is water, increasing the likelihood of contagion.
“If the optimal breeding conditions for mosquitoes are prolonged, for example for two months, they are more likely to reproduce,” he explains.
4. Climate change makes us weaker and our defenses worse.
This happens through several mechanisms.
One of them concerns infrastructure and access to it. For example, “in the event of a hurricane or a flood, the collapse of infrastructure means that we have no access to health services”.
But it also affects us on a physical level.
To name just one, these types of changes generate an alteration in cortisol, the hormone that is activated in the face of danger to, in turn, activate the “defense” or “flight” mechanism.
“It affects our immune system and, in case of infection, we are less able to fight,” says Mora.
Those who “benefit” the most.
Diseases, which range from diarrhea to cardiovascular disease, via encephalitis or dermatitis, have main causes: viruses and bacteria, “those that survive the most”, explains Mr. Mora.
Transmission is mainly through water, air, direct contact or consumption of food.
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Another effect is on our body and the stress that changing weather conditions cause.
“We analyze the effect of climate change on each disease, but not the extent, the way it spreads. Because it already depends on many conditions, such as the culture of the country, the socio-economic conditions or the laws and their valuation, which is complicated to calculate,” explains Mora.
But he points out that quantifying this phenomenon “diverts the blame from the real culprit”, climate change.
“It’s not going to the source and we need to look at what diseases might have been prevented from the start,” he says.
Regarding the diseases included in the study, he said that the focus is normally on infectious diseases, but there are others, such as allergies – he acknowledges that one of the most common is pollen allergy, respiratory diseases and conjunctivitis, which have worsened with climate change and to which attention must be paid.
Although the study points out that some illnesses (just over 60) improved in some cases, “looking for hope is complicated”.
From his home in Valle del Cauca, Mora confesses: “It’s very scary, the amount of suffering that we have seen in our article”.
He notes that what they have studied are cases that have already existed but that it remains to be seen “what will befall us” if action is not taken and politicians “stop thinking with their brains and put their hearts into it.”