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Why climate change may be driving more infectious diseases

People wade through a flooded area in Pakistan, that has been dealing with what people are calling "monster monsoons".
Zahid Hussain
People wade through a flooded area in Pakistan, that has been dealing with what people are calling "monster monsoons".

When discussing the current and future impacts of climate change, the biggest and most visible events like floods and storms may come to mind.

But a new study published this month in the journal Naturereveals that rising temperatures, as well as things like droughts and wildfires, may have a connection with the spread of diseases, including COVID-19.

Camilo Mora is a climate scientist at the University of Hawaii, and is one of the authors of the study that examines the implications of these microscopic shifts.

Mora joined All Things Considered to break down his findings and what this could mean for the future.

This interview has been lightly edited for length and clarity

Interview Highlights

On the link between climate change and diseases

It turns out that just like you and me, every time that we get impacted by one of these climatic hazards, that are becoming more common — a heat wave, a wildfire or whenever there is a flood — all of those things are related to the increasing amount of greenhouse gasses. Just like us, it turns out that many of those species that are damaging to us are also reacting to it.

And what is happening is that there are many ways in which climate change is actually forcing these species to get into contact with us. By increasing those contacts, it turns out that the amount of pathogens that are in the wild, are having a higher chance to come in and make us all sick. What we did in this paper was quantify the magnitude of how big of a deal this is.

One example of this is to imagine that in the middle of the jungle, in the middle of nowhere, there is a bat. That bat obviously has their own pathogens that have been accumulating for hundreds of years. But they are over there and we are over here. So there is never really any contact. There is no risk for us from that bat. Now imagine we are producing greenhouse gasses. We produce a lot of heat. With that heat comes drought and with that drought come wildfires.

Now this bat that was in the middle of the jungle, creating no pain for us, has to fly around to find food, water and sometimes a habitat by flying farther away. Sometimes it comes into contact with us. And that single moment when the animal with that pathogen gets in contact with us is called a spillover. That's it. I mean, it unleashes an incredible amount of human suffering. For instance, what happened with COVID-19.

On if climate change may also limit diseases

It's interesting because, in fact, we found several diseases to be reduced in impact by climate change. But the greater majority [of diseases], 58% of them, can make us sick in 1,000 different ways, and make these diseases worse.

We found that 60% of [diseases] at times can stop being a problem. An example could be drought. In some cases, the lack of water prevents the creation of mosquitoes. And in some places you reduce all of the diseases that are transmitted by mosquitoes. However, there were certain cases in which drought actually makes the diseases from mosquitoes worse, because there is not a lot of water. The limited amount of water that was there is where the mosquitoes will want to reproduce, and so [that water will attract] all of the species that are also around, trying to look for water. So basically it works as a magnet, these little reservoirs of water, for all kinds of pathogens and mosquitoes.

On a potential link between climate change and diseases like Monkeypox and COVID

Oh, the connection is right there. It's just mind blowing. And in fact, I lived it. I came for a holiday in Colombia. And I think I'm a strong guy and, you know, Colombians, we like to feel like we are jungle guys. I refused to use mosquito repellent and I got bitten by a mosquito, but I didn't know that the mosquito had Chikungunya, and I got infected with this disease.

My skin was awful, I blistered there for a week, and it's painful to this day. I had the pain of this on my joints. I came to discover as I was doing this paper, that the reason why that outbreak was happening was because there was so much rain all over South America that it just created these infected mosquitoes all around the world. And it just happened that the Chikungunya, which was pretty rare, in a very remote place with so many mosquitoes, [had reached me].

On the real life pressure of these findings

For me it's shocking, you know, reading all these different papers, and then realizing and putting these things into context, like, "Wow, this thing was there right in front of our faces?" I have to tell you that the motivation for us to do this paper was to see if climate change had something to do with the outbreak of COVID-19. I can tell you up front that we just don't know yet, but what I can tell you after doing this work is that there are at least 20 different ways in which COVID-19 could have been caused by climate change. And that, for me, is the worrisome thing. You know, regardless of whether it is now, climate change has at least 20 different ways in which it can create things as bad as COVID-19.

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Ari Shapiro has been one of the hosts of All Things Considered, NPR's award-winning afternoon newsmagazine, since 2015. During his first two years on the program, listenership to All Things Considered grew at an unprecedented rate, with more people tuning in during a typical quarter-hour than any other program on the radio.
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