“The Last of Us” and Viagra Tibet

Last of us – a new series from HBO, representing a dystopian post-apocalyptic world in which humanity has almost completely disappeared due to an outbreak of a dangerous infection that controls the brain and turns people into bloodthirsty formless monsters.

The series presents two significant differences from typical films such as Night of the Living Dead or the walking Dead: affected people are not “undead” (zombies), but are alive; and the infecting organism is not a virus, but a fungus ophiocordyceps what exists in real life.

Some Manipulative Mushrooms

The creators of the series and the video game on which it is based were inspired by an episode of the documentary. Planet Earth. It contains an entomopathogenic fungus of the genus ophiocordyceps infects a bullet ant (paraponera clavat), whose body he absorbs inside, leaving the brain intact, allowing him to manipulate the insect’s behavior.

Over two hundred species ophiocordyceps which can influence the behavior of insects. They were described in 1931, but, with the exception of Tibetan farmers and the Chinese domestic market, where all kinds of organisms are sold, ophiocordyceps they were total strangers thirty years ago.

The strange case of Chinese athletes

September 1993 Sportswriters were impressed. At the Chinese National Games held in Beijing, all athletes in the 1500, 3000 and 10,000 meter sprints broke the world record. Immediately there was a suspicion of the use of doping substances. The Chinese coach came out on top in an interview published in Athletics news: no drugs. The secret was training at altitude and drinking an ancient tea of ​​traditional Chinese medicine.

It goes without saying that the search for this drink was unleashed, all the more so when it turned out that it also has aphrodisiac properties. It was immediately called “Viagra of Tibet”. The organic basis of the miracle potion was “yarsagumba”, a worm-like mushroom that grows at an altitude of 3000 to 4000 meters above sea level in the Tibetan alpine meadows.

In fact, as if it were a mythological centaur, the yarsagumba is a chimera consisting of the body of a ghostly moth caterpillar. Titarodes armoricanusmummified after being infected with a fungus Ophiocordyceps sinensiswhose mycelium develops from spores existing in the soil.

In autumn, the mycelium infects the living caterpillar, which grows underground and takes root in its body. To grow, the fungus absorbs all of its nutrients from the caterpillar’s body. By the next summer, having eaten it completely, the infection had killed the caterpillar but left its skin intact.

In doing so, the fungus turns into a hardened mass, the sclerotia, which retains the shape of the caterpillar’s body and pushes it head up until it is a few centimeters below the soil surface.

Shortly before the onset of winter, from the head of the caterpillar, which remains buried in the ground, an upright structure emerges from the ground – the stroma. It has some crater-like structures, perithecia, within which spores develop, which will resume the cycle with the onset of autumn, when underground larvae begin to develop, emerging from eggs buried by a butterfly in late spring.

For centuries, this mushroom has been coveted in Asia for its medicinal and aphrodisiac properties. The use of yarsagumba in traditional Chinese medicine has been extensively studied in the East. It has been successfully used in animal studies and in human clinical treatment, among which its therapeutic use stands out as part of the antiretroviral treatment of patients with the HIV virus, which is based on the exclusive active principle of this fungus, the nucleoside didanosine…

Could these fungi cause a pandemic like covid-19?

A fungal pandemic comparable to COVID-19 is unlikely for several reasons.

First, although there are some microscopic fungi that can be fatal when infected, and although some of them appear in cancerous tumors, fortunately, most fungi do not infect humans at all. This does not mean that as many people die each year from fungal infections as from tuberculosis.

For the most part, potentially lethal fungi are opportunistic pathogens. This means that we usually live with them without giving us problems, because they only take root in vulnerable people whose immunity is suppressed by an underlying disease such as cancer, a viral infection such as HIV, and even antibiotic overuse, three factors. which increase the risk of dangerous fungal infections.

Thirdly, most fungi are mesophilic, they grow at low temperatures around 10⁰C, which means that they cannot grow normally at the core temperature of the human body. This is one of the reasons why most fungal infections are usually superficial ringworm.

Everything else ophiocordyceps Known insects are specific to certain insects (whose body temperature is identical to the ambient temperature), they are not adapted to life at our body temperature and cannot compete with our immune system, which is much more complex and developed than that of insects. insect.

WHO report and some recent studies based on near-simultaneous appearance on three continents candida goldenyeasts capable of causing life-threatening infections suggest that climate change may increase the geographic distribution of some pathogens and cause more fungal infections in mammals and humans.

This is what the experts already knew when they predicted it three decades ago. Rising global temperatures mean that fungi must adapt, which could hypothetically increase the number of species potentially causing serious infections in humans.

As one of the characters suggested Last of us, climate change could trigger new pandemic scenarios. Once again, reality can be stranger than fiction.

Manuel Peinado Lorca, University professor. Director of the Royal Botanic Gardens of the University of Alcala, University of Alcala

This article was originally published on The Conversation. Read the original.

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