A deadly ‘superbug’ which has started to infect humans evolved because of global warming, scientists believe.

The fungus, called Candida auris (C.auris), was first identified in Japan in 2009, in the ear canal of a 70-year-old woman and has since spread rapidly around the globe, emerging in five continents, with the first UK case detected in 2013.

Since then it has caused several outbreaks in at least 55 hospitals across Britain, infecting more than 200 patients, and linked to the deaths of eight.

Public health experts are alarmed by the rapid spread of the fungus, has been likened to a ‘superbug’ because it has proved resistant to the main three classes of drug treatment.

But researchers now believe that as global temperatures have warmed, C.auris evolved to thrive in conditions which mirror the internal temperature of the body - 36 to 37C - making humans a perfect breeding ground.

“The reasons that fungal infections are so rare in humans is that most of the fungi in the environment cannot grow at the temperatures of our body,” said lead author Dr Arturo Casadevall, a molecular microbiology expert at Johns Hopkins University.

“Something happened to allow this organism to bubble up and cause disease. We began to look into the possibility that it could be climate change.

“As the climate has gotten warmer, organisms, including Candida auris, have adapted to the higher temperature, and as they adapt, they break through human's protective temperatures.

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

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The fungus, is a type of yeast, which in other forms can cause skin infections. The new type which can lead to deadly bloodstream infections emerged independently in India, South America and Africa.

While healthy patients can usually fend off the fungus, those with compromised immune systems can develop internal infections, which can prove fatal, or cause major disabilities such as hearing loss.

Mammalian are usually resistant to invasive fungal diseases results from a combination of high internal temperatures that create a thermal restriction zone and innate immunity.

Candida auris credit: KATERYNA KON/SCIENCE PHOTO LIBRARY

In the new study, the researchers found that C. auris is capable of growing at higher temperatures than most of its closely related species. Adaption to higher temperatures is one contributing cause for the emergence of C. auris, the researchers conclude and called for better surveillance to monitor new diseases.

“What this study suggests is this is the beginning of fungi adapting to higher temperatures, and we are going to have more and more problems as the century goes on,” added Dr Casadevall.

“Global warming will lead to selection of fungal lineages that are more thermally tolerant, such that they can breach the mammalian thermal restriction zone.”

Global studies have found six in ten of those infected with the C.auris die - though it has not been shown whether the infection has caused the deaths.

Outbreaks in British hospitals have been so bad, that The Royal Brompton Hospital and Harefield NHS Foundation trust in London was forced to close its intensive care unit for two weeks, while 70 patients were infected at the John Radcliffe Hospital’s Neurosciences Intensive Care between 2015 and 2017.

Commenting on the research, Dr David Eyre, Senior Research Fellow and Honorary Consultant in Infectious Diseases & Medical Microbiology, at Oxford University Hospitals said: "What we do know is that it is a fungus that has likely existed for hundreds or thousands of years, but that it has only started being detected as a cause of infections in patients in the last few years.

"Several possible explanations have been suggested including changes in how we deliver healthcare including more use of antifungal drugs that Candida auris has become resistant to, but also changes in the wider environment, e.g. changes in agricultural use of antibiotics/antifungals, and also changing climate has been proposed as you say.

"Candida auris does grow well in the lab at slightly higher temperatures than many other organisms."