Guest essay by Eric Worrall
According to Time Magazine, Climate Change makes future Coronavirus epidemics more likely – though Climate probably wasn’t responsible for the current crisis.
The Wuhan Coronavirus, Climate Change, and Future Epidemics
BY JUSTIN WORLAND 10:52 AM EST
I have no evidence that climate change triggered this particular virus to jump from animals to humans at this particular time, or that a warmer planet has helped it spread. That said, it’s pretty clear that, broadly speaking, climate change is likely to lead to an uptick in future epidemics caused by viruses and other pathogens. Scientists have understood for decades that climate change would change the way diseases spread, but, as the planet warms, those hypotheses are being tested and scientists are learning in real time. There are many links between climate change and infectious diseases, but I’m going to focus on one particularly novel—and concerning—area of knowledge: how rising temperatures are making our natural immune systems less effective.
But, as pathogens are exposed to gradually warmer temperatures in the natural world, they become better equipped to survive the high temperature inside the human body. “Every time we have a very hot day, we have a selection event,” says Arturo Casadevall, a professor of microbiology and immunology at Johns Hopkins University’s Bloomberg School of Public Health. The pathogens that survive—and reproduce—are better adapted to higher temperatures, including those in our bodies. And, with that, one of our body’s primary defense mechanisms diminishes in effectiveness.
This is not a theoretical, far-off concern. Last year, Casadevall and colleagues documented in the journal mBio how Candida auris (a fungus that gets into the bloodstream, leading to a range of ailments) emerged simultaneously in patients in three different isolated places—southern Asia, Venezuela and South Africa—between 2012 and 2015. In our globalized world, diseases are often transported by human carriers who hop on planes, but in this case the scientists concluded that similar changing climatic conditions in each of these places likely drove the simultaneous development. It’s hard to say how widespread this effect could be, Casadevall says, but there’s no reason to think that it would be limited to fungi like Candida auris.
The study quoted suggests that Candida Auris got a foothold in mammals because global warming conditioned a wild fungus to survive temperatures found inside the human body.
The problem with this theory is there are large regions of the world which remain near body temperature all the time, and which did so even in pre-industrial times. At most this region has expanded a hundred miles or so North and South due to global warming.
There were also significant periods of geological history, such as the Eemian Interglacial and the Holocene Optimum, when mammals including hominids experienced extended periods of far warmer temperatures than today.
A more likely explanation for the emergence of a new fungus pathogen is evolution, air travel, and the rise of HIV / AIDS, which provides a large pool of immuno-compromised humans upon whom new pathogens can hone their skills.