Warning 'mushroom pandemic': 1.6 million deaths per year, worrying rate of evolution

Scientists are concerned that fungal infections could be a new pandemic for humans with arguments through the article "Humans are not prepared for a pandemic caused by fungal infections". for pandemics from fungal infections) of National Geographic (USA):

Today, fungal infections are very common. Because mushrooms are everywhere. They live in plants, water, air and soil. While most of these fungi are not harmful, some fungi can cause major infections on our body.

It is worth mentioning that scientists are increasingly realizing that: Changes in the environment and climate today, as well as the overuse of fungicides in agriculture, have fueled the proliferation of fungi capable of ability to infect humans and help them avoid certain drugs designed to kill them.

"What we've been worried about about the fungal world has always been their ability to cause disease in humans," said Tom Chiller, Head of the Mycotic Diseases Branch at the Centers for Disease Control and Prevention. that we don't even understand."

To date, only about 120,000 of the 5,000,000 species of fungi have been identified — of those, only a few hundred known to be harmful to humans.

Worryingly, changes in the environment and climate, as well as the overuse of fungicides in agriculture, have helped create a bacterium capable of 'neutralizing' the 'armour'. (from the immune system) that humans possess to fight them.

Some estimates put the global mortality rate from invasive fungal infections as high as 50%, meaning 1.6 million deaths, and $7.2 billion in medical costs each year. , although these numbers may be underestimated due to ongoing challenges to accurately diagnose cases.

Why are scientists now so afraid of a pandemic involving fungi when fungi have long existed in medicine?

According to Tom Chiller, a number of factors have pushed fungal pathogens into leading pandemics - among them the ability of microorganisms to rapidly grow, an increase in selective pressure forcing them to adapt; Plus an increasing number of people are susceptible to disease.

The vast world of mushrooms

The speed at which mushrooms evolve can startle you.

Amelia Barber, a microbiologist at the Hans Knöll Institute in Germany, recalls the case of a cancer patient who had a Candida glabrata infection of the skin that was resistant to echinocandin — one of the three main antifungal drugs available — within a few days of treatment. "We think this organism is actually part of her microbiome, and by giving her prophylactic drugs to protect her, it was able to become resistant and propagate."

When Amelia Barber sequenced the genes of her patient's fungal samples, 12 days apart, she found that the fungus had acquired both mutations previously known to confer resistance to echinocandin as well as mutations another new variable. Amelia Barber speculates that these additional adjustments have allowed the bacteria to live in the blood after it has spread from the skin, where it normally resides.

"We hypothesized that those changes helped the fungus to cope with the new nutrient environment and also stick around because there was more flow in the blood compared to the skin." This also makes pathogens more virulent - better able to adhere to host cells and release substances to evade the body's immune system."

This virulence [is the way to initiate infection and pathogenicity of microorganisms] is what makes invasive fungal infections dangerous - as opposed to superficial diseases such as fungi. foot skin or thrush.

Color scanning electron microscopy of Aspergillus fumigatus. Although harmless in healthy people, the fungus Aspergillus fumigatus can cause complications in people with respiratory conditions or a weakened immune system. Inhaling Aspergillus fumigatus spores can lead to lung and bronchial infections, which can be fatal in some cases.

Raging fungi excrete tissue-destructive toxins that they can then ingest - similar to how they break down organic matter as part of an ecosystem's nutrient cycle.

Like bacteria, fungi can cause organs to shut down due to sepsis, an overreaction of the immune system to a microbial attack. Or they can form mushroom balls that push the organs aside. Resistance only makes things worse: Mortality rates are 25% higher when pathogens resistant to antifungal drugs are present.

Fungal pathogens account for a significant proportion - up to 80% - of all diseases affecting crops, destroying a third of global crop production each year.

For example, green mold, which mainly attacks apples and pears, can spread rapidly through fruit, starting with soft indentations in the flesh and ending with green-blue spores scattered along the fruit. surface.

Forests across Europe and North America have been ravaged by Dutch elm disease (DED), a beetle-assisted fungus that can cause healthy trees to quickly wither and died.

The problem is this: The liberal use of fungicides in response to these threats has had unintended consequences.

Marin Brewer, a plant pathologist at the University of Georgia (USA), said the application of a common fungicide, such as azoles, has quadrupled in the past 10 years. Similar to the use of antibiotics in livestock, fungicide manufacturers promote their products to farmers as a way to increase crop yields, leading to overuse by farmers. Over time, the overuse of invisible fungicides makes fungal pathogens resistant to fungicides.

This story goes on to face a major problem: "Because the development of new antifungal drugs is a lengthy, expensive, and complex process. Furthermore, because humans and fungi share many genes and genes, So what's toxic to fungi often affects us humans.

That is, developing fungicides whose ingredients are still present in our bodies is a challenge. Currently, there are only three main antifungal drugs that can be used in patients," said Michelle Momany, a plant pathologist at the University of Georgia (USA).

Mushrooms are master adaptogens

Although mutation rates per generation are generally lower in fungi than in bacteria or viruses, fungi are master adaptogens. And fungi have two main tools: Short life cycles and, in some cases, the ability to reproduce sexually and asexually.

Multiple generations of fungi spring up and down in a matter of hours, so mutations can form quickly. But for Marin Brewer, it was the fungi that could reproduce both sexually and asexually that scared her because they had the highest evolutionary potential.

"Fungi can develop resistance to one fungicide developed in one individual; and resistance to another fungicide develop in another. They can then assemble those resistances. that comes together through sexual reproduction and then explodes inside the victim," says Marin Brewer.

Once a mutation is present, the gene containing it can be duplicated many times over, amplifying the fungus's resistance, adds David Fitzpatrick, a mycologist at Maynooth University in Ireland. Or a fungus can inherit an entire extra chromosome with multiple mutations, helping it to survive in extreme environments."

Even "mushrooms may be evolving to accommodate a warming planet," said Arturo Casadevall, a microbiologist and immunologist at Johns Hopkins.

Most of us don't realize that body temperature is a component of the microbial defense system. But the fact that we are so hot relative to the environment means that many organisms cannot thrive at human body temperature. He estimates that more than 90% of fungal species cannot survive near 37 degrees Celsius, instead between 25 and 30 degrees Celsius.

However, as warmer Earth temperatures become more frequent, this is changing. "I'm worried about organisms out there, filled with virulence factors, that can thrive in hot air of 34.35 degrees Celsius."

Candida auris is the first example of a previously unknown pathogenic fungus that emerged as a direct result of climate change. Starting in 2012, Candida auris appeared almost simultaneously on three continents - ready to fend off antifungal attacks and invade its victims.

Candida auris emerged as a direct result of climate change.

"This organism is out there, it's resistant to drugs, and it's capable of surviving at higher temperatures," said Arturo Casadevall.

At present, the mechanism by which this fungus adapts to heat is still unknown and is the subject of scientific research around the world.

Pathogenic fungi remain opportunistic – their danger is mainly limited to vulnerable populations, including the immunocompromised and the elderly.

However, the danger of fungi is that they are constantly evolving to adapt.

Fungi are all around us and play an important role in Earth's ecology - so the goal is to coexist, rather than destroy. Perhaps we should approach the use of fungicides more carefully. Only use them when really needed and use them effectively, not indiscriminately spraying.

'At CDC, we are working proactively to have data on the risks of fungi to human health,' said Tom Chiller, Head of the Mycotic Diseases Branch at the US Centers for Disease Control and Prevention. while taking into account the importance of fungicides to the global food supply, so that fungal diseases do not become a pandemic that wreaks havoc on our plants and human health. To help people be more 'ready' to face any harmful mutations of the fungus!