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How climate change could be impacting pathogenic diseases


We often talk about the impact climate change will have on us in big, visible ways, like floods, fires and storms. A new study published in Nature this month looks at much smaller ways climate change may affect us, microscopic ways. Climate scientist Camilo Mora of the University of Hawaii was one of the authors of the study. And he told me part of their motivation was to see if climate change had anything to do with the outbreak of COVID-19.

CAMILO MORA: We just don't know yet. But what I can tell you after doing this work is that I can tell you at least 20 different ways in which COVID-19 could have been caused by climate change.

SHAPIRO: So I asked him to explain the connection between climate change and diseases caused by microorganisms like viruses and bacteria.

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

SHAPIRO: Give us one story, one example, that illustrates how this works.

MORA: So one example that I like very much is imagine that in the middle of the jungle, in the middle of nowhere, there is a bat. And that bat obviously has their own pathogens that they have been accumulating for hundreds of years. But they are over there, and we are over here. So there is never really a contact. There is no risk for us from that bat.

Now imagine we producing greenhouse gases. We produce a lot of heat. With that heat comes drought. And with that drought comes, at times, wildfires. Now this bat that is in the middle of the jungle in the middle of nowhere, creating no pain to us, has to fly around to find food, water and sometimes habitat by it flying farther away. Sometimes it comes into contact with us. And that single moment, when the animal with the pathogen get in contact with us is called a spillover. And from there, once that spillover happens, that's it. I mean, that unleashes an incredible amount of human suffering, like, just like, for instance, what had happened with COVID-19.

SHAPIRO: So the top-line takeaway is that climate change is going to make us more or less susceptible to these kinds of diseases?

MORA: The way that I put it is like, imagine that I am going to get into a fight with Mike Tyson. Now, on top of that picture, put three other fighters like Arnold Schwarzenegger (laughter), Sylvester Stallone and Jackie Chan. And now you have those...

SHAPIRO: Mike Tyson, Arnold Schwarzenegger, Jackie Chan and Sylvester Stallone? OK.

MORA: Oh no, I think that can beat my - they can kick my butt, for sure.


MORA: The analogy goes that I cannot endure one of them; forget about enduring the four of it. You can see heat waves everywhere around the world, wildfires, floods, you name it. That's nothing compared to what is coming. Right now, the planet has warmed up by just one degree. And we predict that in worst-case scenario, it could warm up to five. So take all of these things that we think are bad, multiply by five, and that's how potentially bad could this be.

SHAPIRO: Even if all carbon emissions stop tomorrow, the Earth will still continue heating up from the decades of human activity up to now. So how do infectious disease experts need to adapt to a planet that will warm no matter what we do?

MORA: The priority should be on mitigation of these problem because, yeah, you are right, we - this is going to be bad. But what I am saying to you is if we don't do anything, this is going to be a lot worse. The chances that we're going to be able to adapt to these are going to be so overwhelming. Just think about what it costs us to adapt to COVID. Those are 1 in a 1,000 years diseases. Imagine these things happening every 10, every 15 years. We are not going to be able to cope with this.

SHAPIRO: When you look at the diseases that we're struggling with right now, from COVID to monkeypox to polio, do you see a climate change connection?

MORA: Oh, the connection is right there. It's just mind-blowing. And in fact, I live it. I lived through that in my own country back in the day. I came for a holiday in...

SHAPIRO: Colombia.

MORA: ...In Colombia. And I thinking that I'm a strong guy. And, you know, Colombians, we like to feel like we are the jungle guys. And I come here, and I refused to use mosquito repellent. And I get bitten by a mosquito. It turns out that that mosquito had chikungunya. And I got infected with this disease. My skin is all full of blisters for a week. It was painful. To this day, I have the pain of this on my joints.

Come to discover, as I was doing this paper, that the reason why that outbreak was happening was because there was so much rain on all of America that it just created this bloom of mosquitoes around the world. And it just happened that the chikungunya, which was pretty rare in a very remote place, with so many mosquitoes, the chances were there for that virus to go and infect everybody. And I paid the consequences of this.

SHAPIRO: Camilo Mora is a climate scientist at the University of Hawaii, speaking with us from Colombia. Thank you very much.

MORA: Thank you very much. I really appreciate it. Transcript provided by NPR, Copyright NPR.

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.
Megan Lim