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Climate crisis might be behind the rise of mysterious superbug C. auris, study suggests

Posted at 8:00 AM, Jul 23, 2019

The climate crisis may be to blame for the mysterious spread of a multidrug-resistant superbug, Candida auris, according to a study published Tuesday.

Until recently, scientists considered it a mystery how C. auris popped up in more than 30 countries around the globe a decade after it was first discovered in 2009 . It emerged simultaneously on three continents -- in India, Venezuela and South Africa -- between 2012 and 2015, each strain being genetically distinct.

The new study, published in the journal mBio, says this serious public health threat may be the first example of a new fungal disease emerging because of the climate crisis.

"The argument that we are making based on comparison to other close relative fungi is that as the climate has gotten warmer, some of these organisms, including Candida auris, have adapted to the higher temperature, and as they adapt, they break through human's protective temperatures," said co-author Dr. Arturo Casadevall , chairman of molecular microbiology and immunology at Johns Hopkins Bloomberg School of Public Health.

"Global warming may lead to new fungal diseases that we don't even know about right now."

Experts have warned that the climate crisis could "halt and reverse" progress made in human health.

For the study, researchers looked at the thermal susceptibility of C. auris and found that it was able to adapt and grow at higher temperatures than many of its fungi relatives are able to tolerate.

This study theorizes that C. auris was an environmental fungus initially found in wetlands and may have had an intermediate host like a sea bird and then been passed to humans.

Fungal infections are relatively rare in humans because the fungi can't grow in the body's temperature range and because of the body's natural host defense mechanisms.

Earlier studies have shown that of the millions of species of fungi, only a few hundred cause human disease.

Severe cases of this superbug can cause a blood infection in some patients according to the US Centers for Disease Control and Prevention and it poses a "serious global health threat."

The fungus can linger on medical equipment at health care and long-term care facilities and can transfer from one person to another, earlier studies have shown.

Since there may be other factors that have led to the emergence of this superbug, the authors suggest more research is needed.

A study published earlier this year suggested that a change in climate conditions could change the environmental spread of fungi and influence its ability to infect others, but "given an absence of knowledge about its natural habitat, it is impossible at this time to determine whether climatic changes played a role in its recent emergence as a human pathogen."

Other studies have blamed the widespread use of antifungal drugs, but the latest study argues the theory does not easily explain why it suddenly became a human pathogen on three continents.

But regardless, better surveillance systems are needed to look for fungal infections like C. auris, authors said. Unless illnesses are reported in medical literature, scientists won't know the fungi is spreading.