The Fungus Among Us

HBO has a new hit series on its hands. “Last of Us” is based on the critically acclaimed video game series of the same name. This franchise takes place in a zombie apocalypse. But what makes this zombie show different from others is the source of infection: fungi. Creators consulted with mycologists (fungi scientists) to explore the possibility of what might happen if fungi had the ability to parasitize humans in the same way they parasitize invertebrates.

The fungus responsible is from the Cordyceps genus. And while this is a real genus of parasitic fungi, it only infects invertebrates. “Last of Us” begins with the premise of climate change causing fungi to evolve to survive in warm-bodied hosts. Diseases in other animals do sometimes lead to infections in humans. Avian influenza is a recent example of concern, and the Centers for Disease Control has a long list of other diseases. But it would take a massive leap in evolution for Cordyceps fungi to infect any mammal, let alone humans.

So how do these fungi work in reality? Species from the related Ophiocordyceps genus can alter the behavior of insects and spiders to serve the needs of the fungi – primarily the ability to reproduce through spore dispersal. There are more than 200 described species of Ophiocordyceps. The genus was first described in 1931.

Ophiocordyceps unilateralis (previously called Cordyceps unilateralis) specifically targets ants, causing them to climb up plants and hang from the undersides of leaves. Once there, a fungal protrusion grows on the ant’s head and eventually disperses spores for reproduction. This process ultimately kills the host ant.

Ophiocordyceps sinensis targets ghost moth caterpillars on the Tibetan Plateau and the Himalayan regions of Bhutan and Nepal. The fruiting body of the fungi is highly valued in traditional Chinese medicine. The fungi, still attached to caterpillar bodies, are hand-collected. Known as yartsa gunbu in Tibet, a single kilogram can fetch more than $18,000. High prices and high demand have led to political conflict as well as habitat degradation, making this species Vulnerable in the IUCN Red List of Threatened Species™.

Then there is an unrelated parasitic fungus that made headlines in 2021 at the height of the Brood X cicada boom. Massospora cicadina turns some cicadas into “single-minded sex machines—after causing their genitals to fall off,” as described in a Scientific American article.

All of this is to say that fungi are FASCINATING! And yet there’s still so much we don’t know. The greatest threat to fungi is actually our lack of information, and these gaps in knowledge put species at risk of extinction. We explored this issue in a video produced in partnership with the IUCN Species Survival Commission’s Fungal Conservation Committee.

This blog is a collaboration between experts at the Global Center for Species Survival, including Plants & Fungi Conservation Coordinator Cátia Canteiro.

Published January 22, 2023