HBO drama ‘The Last of Us’ is not just an exaggeration
It’s 2003, and Cordyceps, a type of fungus that belongs to Cordyceps, makes the leap from ants to humans, transforming its hosts into bloodthirsty zombies that infect everyone they bite. The solution proposed by the best fungi (a scientific term for fungus) in Jakarta, Indonesia, where the case was reported, was radical: to bomb the entire city and everyone in it, erasing any traces of infection.
This is the content of the HBO drama ‘The Last of Us’, which was released last month and drew praise from the public and critics at the same time. The show posits that the greatest threat to human society is not viruses or bacteria, but molds beloved by brewers, bakers and wild food lovers. Specifically, Ophiocordyceps unilateralis, known as the “zombie ant fungus,” turns humans into alternate hosts as part of its adaptation to survive higher temperatures in line with climate change.
Craig Marzin, writer and producer of the HBO miniseries Chernobyl, who worked on the work, argued that it makes no sense that these fungi are adapting to manipulating the ants’ brains to propagate their spores. It is possible to steal a human heart just like stealing an ant’s heart.
The British Guardian reported on the 10th (local time) that the real threat of mold cannot be ignored to dismiss this as science fiction imagination. Fungal infections already claim about 2 million lives each year. This is more than the number of people who fall victim to tuberculosis or malaria. To make matters worse, these fungi are becoming increasingly resistant to currently available antifungal agents, and there are no new antifungal agents under development. There is no antifungal vaccine.
The World Health Organization (WHO) published a list of the 19 fungi most dangerous to humans last October. The report that published the list noted that “despite the fact that fungal infections pose an increasingly significant threat to human health, they receive little attention and resources worldwide.”
Fungi are the most numerous organisms on Earth, with an estimated 12 million species worldwide. Most of them are not even classified. About 1 billion people are infected with the fungus each year, although only a small fraction of them infect humans. Professor Mark Ramsdale of the MRC Center for Mycology at the University of Exeter, UK, said: “Most of these are superficial things like athlete’s foot, but it’s a life-threatening fungus that is a problem for people who are very old, very young or at high risk with a weak immune system.” Although these fungi are underestimated because they primarily infect people with serious health problems, they claim 1.5 million deaths per year, he said.
At the top of the WHO’s list of killer fungi are three types of pathogenic yeast and a fungus called Aspergillus fumigatus, commonly found in soil and decaying vegetation. Human Immunodeficiency Virus (HIV) and chronic lung disease, or aspergillosis caused by infection with the fungus in people such as organ transplant recipients, can be life-threatening.
Some of the fungi on the WHO list can even affect healthy people. Coccidioides, also known as “coccies,” are soil fungi that live in the southwestern United States, Mexico, and parts of South America. Some people who inhale it develop a flu-like illness called ‘valley fever’. Up to 10% of infected people develop severe lung disease, and about 1% will die. In the United States, about 150,000 people are infected each year and about 75 people die from it.
The range of coxi infection is also widening. Valley fever has recently been detected as far north as Washington State, which borders Canada. The number of reported infections also increased by 400% between 1998 and 2015, which climate change is being blamed for.
It seems that other fungal infections have increased due to corona. Aspergillosis and mucosal mycosis, ‘black fungus syndrome’. These fungal infections often occur in people with compromised immunity or lung damage. Doctors are seeing an increase in these fungal infections as lung damage from infections with the coronavirus increases.
In particular, the symptoms of mucosal mycosis are terrifying. It starts in the nostrils and spreads to surrounding tissues and organs, including the eyes and brain, causing darkening of the skin, swelling of the face, blurred vision, altered consciousness or coma. Some patients may lose sight in both eyes or require surgery to remove infected bone and tissue.
Although fungal diseases are scary, they do have one advantage. Most of them are not contagious from person to person. Rather, they grow only in special environments where their spread is limited. Mucormycosis, for example, is 70 to 80 times more prevalent in India than in other parts of the world.
Every rule has exceptions. One of them is a fungus of the genus Candida. A relative of yeast that causes thrush, it is a dangerous species on the WHO’s grave threat list because it quickly neutralizes antifungal drugs developed by mankind. Like other fungi, it mainly preys on people with weak immunity, and if it enters the blood or other organs, the infected person has a 50/50 chance of survival.
Like the fungi in ‘The Last of Us,’ fungi of the genus Candida have recently appeared in humans. Its existence was first revealed in 2009 when it was found in the ear canal of a 70-year-old Japanese woman in Tokyo. But within a few years, cases of infection with the fungus were being reported across Asia, Africa and the Middle East.
Professor Matthew Fisher from the MRC Center for Global Infectious Disease Analysis at Imperial College London (ICL) in the UK said, “It is an absolute nightmare in hospitals because it is currently prevalent worldwide and is resistant to many frontline antifungal drugs.” It is also partially resistant to disinfectants and heat, making eradication extremely difficult. If this mold is found, the entire ward will be temporarily closed.
It is not known where Candida fungi come from. “I’m guessing it’s just one of the myriad fungi out there,” Fisher said. Climate change may have moved them from an unknown host to us. Rising temperatures may have promoted mutations that can grow at human body temperature.
Another possibility is that overuse of antifungal drugs has inhibited the growth of competing organisms, opening a niche for fungi such as Candida that are resistant to antifungal drugs to thrive. Complicating matters further is the fact that there are only four antifungals, and none are being developed.
“Fungi are in fact very closely related to animals, so drugs that can interfere with fungal growth and development are often toxic to humans,” Ramsdale said. Despite these concerns, fungi currently account for less than 1.5% of all infectious disease research funds. The WHO report calls for increased surveillance and development of antifungals, as well as better diagnostic tools, so that patients can be treated quickly with the right medications. “Even in medical school, there are only one or two lectures (on fungal pathogens),” Ramsdale said.
The threat of mold is not limited to humans. There are an estimated 6,000 species of fungi that cause disease in commercial crops alone. Every year, 40% of the world’s rice harvest is lost to rice blast, which is also a fungal infection. The threat of mold is directly related to the threat to food security.
The WHO report does not address threats that have not yet made the leap to humans. Conservation biologists have watched helplessly as 500 amphibian species have declined and 90 species have gone extinct since the 1990s, caused by fungi called chytrid fungi. The scenario imagined in ‘The Last of Us’ has already occurred in amphibians.
But mold can present as much opportunity as it poses a threat. Penicillin, the world’s first antibiotic, was discovered in a fungus. Who knows what chemical secrets these mycelium hides?