Global warming is fueling the rise of dangerous fungal infections

Heat

Regarding the multidrug-resistant mushroom Candida aurisFew things are going well According to the CDC, several countries have reported that this fungus (technically, a yeast) is causing serious illness in hospitalized patients. C. auris is difficult to detect with standard equipment, can cause dramatic epidemics (especially in hospitals) and is extremely difficult to treat.

To make matters worse, global warming makes treatment even harder, researchers say.

"The argument we make on the basis of comparison with other nearby fungi is that, when the climate warmed up, some of these organisms, including Candida auris, adapted to the higher temperature and pierced the protective laws of the human. temperatures, "said Arturo Casadevall, MD, Ph.D., president, molecular microbiology and immunology, Johns Hopkins Bloomberg School of Public Health, Baltimore, Maryland. "Global warming could lead to new fungal diseases that we do not even know about yet."

The idea that climate change brings up more diseases is not new. For starters, some pathogens hidden in permafrost ice begin to wake up as the ice melts. It's unclear how much impact it will have, but it raises legitimate concerns. Secondly, rising temperatures and changing weather conditions are increasing the range of disease-carrying insects, particularly mosquitoes. Malaria and West Nile virus are starting to spread to new areas as mosquitoes adapt to previously inaccessible habitats. Third, as is the case here, rising temperatures help pathogens bypbad our body's natural defenses.

Dr. Casadevall explains:

"The reason why fungal infections are so rare in humans is that most environmental fungi can not grow at the temperature of our bodies."

Our body temperature is not a random result of evolution. Recent studies have suggested that it was a perfect balance – warm enough to prevent fungal infections, but not too hot for us to have metabolic problems. Not only humans: all mammals are generally resistant to fungal diseases because of high body temperature (compared to other creatures), which are effective defense mechanisms.

However, global warming could deprive us of it.

Strange yeasts (and where to find them)

A proposed scheme for the emergence of C. auris, favored by global warming and urbanization. Image credits: Casadevall et al / mBio.

Most mushrooms are found in a variety of places – soil, insects, plants, animals – but the only place C. auris has been found so far is in people. Thus, our bodies and pathogens are in constant struggle and rising temperatures give the mushroom advantage.

Pathogenic fungi for humans are only a very small minority of all mushrooms, but this is not the strangest thing.

"The most enigmatic aspect of the rise of Candida auris as a human pathogen is that it has appeared simultaneously on three continents, with each clade being genetically distinct," the researchers write.

Fundamentally, C. auris seems to have evolved independently on three continents: India, South Africa and South America. It is unclear exactly how (and why) this happened, especially since the researchers only isolated the first specimens in 2009. Another thing that is not clear about this is its dangerousness.

According to the CDC, C. auris can kill 30 to 60% of infected people, which seems absolutely horrible. However, at least in developed countries, it seems to only affect people already suffering from serious diseases (such as those placed in intensive care units). It is difficult to say how much of the damage is caused by the pathogen itself and under what conditions.

Whatever the case may be, rising temperatures help the yeast.

In the new study, the researchers compared the thermal susceptibility of C. auris to some of his closest relatives. They found that C. auris is able to grow at higher temperatures than most of his parents. According to the team, adaptation to higher temperatures is one of the causes of the emergence of C. auris, and global warming is probably one of the main contributors.

The team calls for more follow-up and study of C. auris as well as its non-pathogenic parents, to better understand its dangers and learn new ways to combat them, while adapting to global warming. The researchers point out that while global warming is an important factor for the emergence of this yeast, it does not say everything.

"Although environmental changes related to global warming may have played an important role in the emergence of C. auris, it is unlikely that this variable explains everything," the study concludes.

The study was published in the journal mBio