Rise of candida auris blamed on global warming

13Nov 2020
The Guardian
Rise of candida auris blamed on global warming

Candida auris is a species of fungus that grows as yeast.  It is one of the few species of the genus Candida which cause candidiasis in humans. Often, candidiasis is acquired in hospitals by patients with weakened immune systems. 

It has attracted widespread attention because of its multiple drug resistance. Treatment is also complicated because it is easily misidentified as other Candida species.Global warming may have played a pivotal role in the emergence of Candida auris, according to a new study. C. auris, which is often multi-drug resistant and is a serious public health threat, may be the first example of a new fungal disease emerging from climate change.

Scientists have a new theory about the origins of a dangerous, drug-resistant fungus that can strike the sickest patients in hospitals and other facilities that provide long-term care: global warming.

The fungus, a type of yeast called candida auris, was discovered just 10 years ago in a Japanese patient with an ear infection. ( auris is Latin for  ear. ) Since then, it has been diagnosed in patients around the world.

But  candida auris didn't spread like a virus would, radiating out from one location. Instead, it popped up simultaneously in different parts of the world, including India, South Africa and South America.

"It was really mystifying that Candida auris appeared at the same time in three continents," said lead study author Dr. Arturo Casadevall, chair of the molecular microbiology and immunology department at the Johns Hopkins Bloomberg School of Public Health. Casadevall and his team thought the fungus's emergence must have been the result of some kind of change in the Earth's environment — in this case, a gradual rise in temperature.

That's odd for fungi, which generally like ambient, cooler temperatures, like a cool forest floor where you might find a toadstool. Indeed, most fungal infections in people are found on the coolest parts of the human body, including the feet and in nail beds. The fungus tends to stay on the skin and doesn't cause an internal infection because it can't survive the warmer temperatures inside the body, where it is around 98 degrees Fahrenheit.

Candida auris is different. While it poses no threat to most healthy people, it can survive inside the bodies of very sick people with weakened immune systems and cause serious complications.

Casadevall's research involved what's called a phylogenetic analysis of C. auris and its closest relatives in the fungi world.The researchers compared different types of fungus related to C. auris, looking at whether each fungus could survive at higher temperatures. C. auris was the only one that was able to do it effectively.

The teams says it's evidence that fungi have begun to adapt to live at hotter temperatures. In theory, that makes them much more likely to make the jump from living on cooler skin, to warmer temperatures inside the body.

C. auris first showed up in the United States in 2016. Since then, the Centres for Disease Control and Prevention have recorded 716 cases of the infection.  

Climate change has been implicated in other changes in disease-causing pathogens, especially bacteria that like to live in warm water, and the spread of mosquito-borne viruses such as Zika and West Nile. And a recent report from the CDC also suggested climate change has played a role in the emergence of drug-resistant fungal infections.

But because scientists do not yet know where C. auris first came from, it's difficult, if not impossible, to prove the link. Still, the fungus is now found worldwide, and cases continue to mount. "The fungal world is underappreciated and understudied," Casadevall said. "What's protecting us is our temperature immunity."

"If more of these organisms become temperature resistant," he said, "then we're going have more problems in the future."