Many of us have watched The Last of Us, which depicts a post-apocalyptic world where a fungal infestation has destroyed civilization. Some believe this would come into reality. How true is that?
The deadly fungus is inspired by the real-life insect infecting Cordyceps zombie fungus. Infected insects' nerve systems are taken over by the Cordyceps fungus, leaving them powerless and finally bursting from their bodies.
Though the possibility of a rapid fungal pandemic is low, it is important to note that fungi are still a major threat to human health. Fungi make up a huge portion of the animal kingdom, with over three million recognised species. Fungi prefer temperatures closer to 10 °C, making them unlikely to thrive at the 37 °C found inside a human body. Because of this, most fungal infections in humans are found only on the skin's colder outer layers.
In addition, this is why, despite the vastness of the fungal world, only a small subset of these organisms may cause infections in humans. Yet some of the most dangerous types of fungus flourish in warmer climates. Yeasts like Candida can be a normal component of our gut flora, but they can cause significant illness if they make their way into the bloodstream and other body tissues.
New challenges may arise because of climate change, as one of the characters in The Last of Us indicates. Fungi must change in response to rising temperatures worldwide. Potentially, this might lead to a rise in the diversity of organisms capable of causing fatal human illnesses. Some indicators point to the possibility that this is already taking place.
Although just four types of antifungal drugs are now available, the health service warns that fungal diseases pose a serious threat to public health due to their rising prevalence and resistance to treatment. Fast and accurate diagnostics for most fungal infections are either unavailable or too expensive.
WHO's associate director-general for antimicrobial resistance, Dr. Hanan Balkhy, adds, "Fungal infections are spreading and are becoming increasingly resistant to treatments, making them a public health problem globally."
Patients with compromised immune systems and those already in critical condition are at the most risk from invasive fungal infections. Cancer, HIV/Aids, and chronic respiratory illness patients, as well as those receiving organ transplants, are among the most vulnerable groups.
However, the Global Action Fund for Fungal Infections reports that every year more than 300 million individuals contract a fungal infection, and 1.6 million people die from their symptoms. In addition, it warns that another 25 million people are in grave danger of dying or going blind. Disabling fungal epidemics have been documented across the world, including in the United Kingdom.
As a bonus, because of how fungal infections begin, they seldom transfer from one person to another. Inhaling fungal spores from the air is the initial step in the development of many life-threatening fungal illnesses. Because our immune system efficiently destroys fungus spores, humans hardly become sick even after inhaling hundreds every day. Even the brain can become a target for a serious fungal infection that begins in the lungs.
Fungal brain infections are the worst. The fungal infection known as Cryptococcal meningitis is responsible for most of these cases. Nonetheless, fungi-possessed zombie ants do exist. Approximately 14 years ago, Sir David Attenborough was the initial person to comment on the occurrence in a film shown on BBC Earth.
As the title suggests, it depicts the Cordyceps fungus infiltrating the "bodies and minds" of bullet ants in the South American rainforest. And it gets much, much scarier because many other species are also shown to be susceptible.
Sir David notes disturbingly, "There are hundreds of distinct forms of Cordyceps mushrooms and, surprisingly, each specialises in only one species."
No, we probably don't have to worry about zombie Cordyceps fungus evolving to infect humans as it does in The Last of Us any time soon, though there are fungal illnesses that can move to the brain. Cordyceps cannot simultaneously infiltrate the human brain and nervous system because it is not designed to develop at our internal body temperature and cannot compete with our immune system, which is significantly more sophisticated than an insect's. It would need thousands of years of evolution to be able to overcome this.
Even while it's highly improbable that fungal infections would trigger a global pandemic or zombie apocalypse, they nonetheless warrant worry. Since the 1960s, there has been a steady increase in the incidence of fatal fungal infections among the general population. This is worrisome since antifungals are far less common than antibiotics, severely limiting our ability to treat fungal infections.
It's challenging to create these medicines since fungus and human bodies have comparable biochemistry. We are also vulnerable due to the proliferation of fungi that have developed resistance to antifungal drugs. More research on the possible risks posed by fungus is required immediately.
The prevalence and distribution of fungal illnesses also appear to be increasing. For instance, the oral and vaginal thrush-causing Candida fungus has evolved to be more difficult to cure and more ubiquitous over time. It wasn't until last month that a strain of the bug that was resistant to treatment was discovered in Mississippi.
In the recent decade, the extremely dangerous infection has spread rapidly across the United States, threatening the health of those with compromised immune systems.
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