The popular HBO drama series "The Last of Us" instilled images of fungal devastation in the minds of millions. But while a fungal pandemic is a real possibility, the reality of it would look much different than the TV show or video game.
Indeed, thanks to "The Last of Us" and other recently alarming fungal public health news, fungi are progressively centering themselves in public health threats — an alarming trend that could foster a pandemic unlike anything seen before. For now, that risk is relatively low. But of all the microorganisms that attack humans, fungi are some of the most threatening, largely because we know so little about them and have few tools to monitor them or fight back.
In its first-ever global effort to rank fungal pathogens by threat level, the WHO released a call-to-action in October 2022, urging public health agencies to pay more attention to fungi's growing perils.
Thankfully, there has never been a major fungal pandemic like we've seen with swine flu (H1N1) or COVID. But there's nothing entirely ruling out such a scenario, either. Humans often can and do get sick with fungi, which can easily kill some people, especially elderly, very young or immunocompromised folks. Public health experts are becoming increasingly vocal about the lack of research or surveillance of these fungal hazards.
For the most part, "The Last of Us" was an inaccurate depiction of a fungal pandemic. For one, many of the most worrisome fungi are microscopic. They also won't turn humans into zombies.
But in some ways, the real-life fungi that can attack human health are more terrifying than cinematic monsters. From eating holes in people's brains to generating nasty tumors to putting folks in comas, some fungi are not to be trifled with. (Others are delicious and definitely should be truffled with.)
One of the biggest problems with a fungal pandemic is we don't have a lot of tools to fight infections. Few antifungal drugs are approved for use in humans, despite the fact that around 150 million infections occur annually, resulting in some 1.7 million deaths per year.
In its first-ever global effort to rank fungal pathogens by threat level, the World Health Organization (WHO) released a call-to-action in October 2022, urging public health agencies to pay more attention to fungi's growing perils.
"Despite the growing concern, fungal infections receive very little attention and resources, leading to a paucity of quality data on fungal disease distribution and antifungal resistance patterns," the WHO warned. "Consequently, it is impossible to estimate their exact burden."
In their report, the WHO categorized 19 fungi that pose a major threat to global health. Here are some that top the list.
We typically think of yeast as the stuff that makes our bread or beer, but Cryptococcus neoformans is a fungi that is the opposite of fun. When it infects someone, it causes a disease called cryptococcosis — which, despite the name, is not a illness conctracted by listening to tech bros rant about Ethereum. Not only can this yeast damage the lungs, causing chest pains and coughing up blood, it can spread into the bloodstream and the central nervous system (CNS). From there, it can create abscesses in the brain that elicit strokes and dementia or carve lesions into the spinal cord.
It kills between 41 and 61 percent of patients it infects, and is especially deadly for people with HIV, cirrhosis (liver disease) or weakened immune systems. Those that survive can expect to spend an average of 18 days in the hospital. There is no vaccine, but it can be treated with the antifungal medications like fluconazole and amphotericin B. However, some of these drugs are unavailable in many countries and the fungi may be evolving resistance to them. One bit of good news is that humans can't spread C. neoformans to other humans, which would prevent an outbreak from getting especially large, but it's no less detrimental.
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Candida auris is another type of yeast, but it generally isn't a threat to healthy people. When it does attack, however, it can be highly fatal, infecting the blood, heart, CNS and even the eyes and bones. As such, it's especially bad for immunocompromised patients, such as those with cancer or recipients of bone marrow and organ transplants. The disease, called candidiasis, often requires months of hospital stays and is fatal in 29 to 53 percent of patients.
More and more hospitals are experiencing outbreaks of C. auris, which is complicated by difficulties in identifying this pathogen and the fact that it is inherently resistant to many antifungal drugs. There is no vaccine.
On March 20, 2023 the Centers for Disease Control and Prevention released a bulletin concerning an "alarming" rise in outbreaks at U.S. healthcare facilities between 2020 and 2021. The report detailed nearly 11,000 cases since 2016, with 3,270 causing infection. (The fungi was detected in the rest, but wasn't causing illness.)
"The rapid rise and geographic spread of cases is concerning and emphasizes the need for continued surveillance, expanded lab capacity, quicker diagnostic tests, and adherence to proven infection prevention and control," Dr. Meghan Lyman, a CDC epidemiologist, said in a statement.
The CDC notes that the COVID pandemic may be the catalyst behind the rise in cases, as it put a lot more people in the hospital, giving the fungi more opportunity to spread. The increase could also be due to increased detection methods. At any rate, the agency said it is expanding its testing capacity for C. auris from seven labs to more than 26 labs nationwide, so we can keep a closer eye on it.
Aspergillus fumigatus is a grayish-green mold that gets its weird name from the shape of its spore-producing structures, which resemble an aspergillum, a Christian liturgical tool used to sprinkle holy water. (It won't surprise you that an 18th century priest came up with this one.) But you wouldn't want to be sprinkled with this fungi. If it got into your lungs, it could cause serious respiratory problems. The fungus is also able to spread through the central nervous system and the brain.
The critically ill are especially vulnerable, especially immunocompromised patients or those with lung diseases, cancers or transplants. It has an extremely high fatality rate, ranging from 47 to 88 percent. Some studies even report a 100 percent fatality rate. There is no vaccine. Even more alarming, A. fumigatus is steadily gaining resistance to a class of antifungal drugs called azoles, which can partially be blamed on their prolific use in farming practices.
"Antifungal resistance is on the rise," the WHO reported. "Widespread use of azole fungicides in agriculture to prevent crop losses is contributing to the rising rates of resistant aspergillosis in humans."
If you're less of a fan of yeast after reading this article, we'd understand. But actually this yeast, Candida albicans, is more of an antihero than an outright villain. Chances are, you have some C. albicans in your guts right now. This fungi naturally coexists with humans, generally doing no harm.
But every once in a while, typically following an illness that degrades the intestinal lining, too much of this fungi will spread into other tissues in the body. This increases the risk of bowel cancers and can infect everything from the blood and heart to the eyes, bones and internal organs. These infections, known as invasive candidiasis, have a mortality rate between 20 and 50 percent, even though resistance to antifungal drugs is relatively uncommon. Nonetheless, resistance seems to be on the rise and no vaccine is available, so we need a lot more data on how prevalent these and many other pathogenic fungi are.
It's difficult to calculate just how much of a risk these fungi pose from a pandemic perspective. On an individual level, however, the fact that more and more people are contracting illnesses from fungi is justified cause for concern. The WHO and the CDC both recommend increasing our capacity for detecting fungi as well conducting more research into treatments. While it is unlikely fungi will ever outpace basteria or viruses in terms of how serious they are to public health, we shouldn't underestimate how disastrous these mushroom-related organisms can be to us.
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