The HBO show The Last of US is adapted from a video game of the same name. TL;DR- zombie apocalypse, but this time the microbe causing the end of humanity isn’t viral or bacterial, it’s a fungus. It’s a good heartwarming family tale of shooting sentient mushrooms.
In this era of 37 concurrent pandemics, what are the odds of adding a few deeply upsetting spores to the list?
Today’s Moment of Science… What’s the matter, ain’t I a fungi?
The 600 someodd known species of Cordyceps vary quite a bit from one to the next, but there’s a major commonality within the genus; they’re all goddamn parasites. Some cannibalize their fellow fungi. Most hijack their species’ preferred insects to do their grim undertaking.
After a spore lands on an unlucky ant, thread-like mycelium can rapidly expand into a network through the insect’s body. Scans have shown fungal cells to be ubiquitous throughout the ant after infection. Tendrils thread themselves all the way down the legs, in between muscle fibers, and the area right outside the brain is positively choked with fungal junk (my band name).
There’s one major major exception to this. The ant’s brain is physically unscathed, keeping it conscious to experience its personal zombie apocalypse.
When the parasite is good and ready, it compels the ant to hike about 25cm up the closest acceptable plant to a zone where the conditions are cozy for fungal growth. Once there, the ant chomps down into the plant and won’t release this mandibular death grip for the rest of its short life. The fungus anchors itself to the plant and bursts out of the lifeless ant’s head, showering spores on their next victims.
This whole process generally takes between four and fourteen days.
Studies suggest cordyceps produce toxins that interfere with their hosts’ sense of smell, biological clock, and foraging abilities amongst other things. It’s a biologically complex jig of death and researchers are still investigating a few steps. On the other hand, the mechanism that causes the ant’s final bite is a bit more direct; fungus just goddamn barges into the muscle fibers, damaging them and forcing them to contract shut, forever.
This all seems miserable for ants and wasps and aphids and idk, like four other insects. But what about us? Well.
We almost certainly will not have to deal with the Cordyceps apocalypse. Given the hundreds of species we’ve identified and how they tend to infect specific insects, the jump to suddenly infecting humans seems highly unlikely.
But, paraphrasing the show’s co-creator Craig Mazin, every scary thing the show says that fungus can do, it does. Not this particular fungus and not to humans, but there are some fungal monsters waiting for us out there.
In 2019 I read warnings about a ‘grab those ankles and kiss yer ass goodbye’ infectious fungus. Then COVID happened and it was all ‘fungus schmungus’ for a bit there. Candida auris makes itself at home in the ear and packs a 30-60% fatality rate. For folks keeping track at home, this is deadlier than smallpox or the goddamn plague.
There were approximately 2,000 cases through 28 states in the last year, including a pretty rough outbreak at two of the largest hospitals in Las Vegas. What happens in Vegas colonizes your ear canal and goddamn kills you.
It’s not the only dangerous fucker from the mushroom kingdom. The WHO’s critical group of deadly fungal infections also includes Aspergillus fumigatus, Candida albicans, and Cryptococcus neoformans. Though it’s more typical for these to infect immunocompromised people, they can be less picky if the mood strikes. Their fatality rates are– technical term– too damn high.
All that said, these stories of a fantastical fungus evolving into a human contagion lean heavily on the ‘fiction’ aspect of science fiction. The odds of an impending zombie apocalypse is AAAAAAAAHHHHHHHHHHH WHAT ARE YOU DOING? NO! GET BACK YOU WALKING MUSHRO….
This has been your moment of brains. Brains. Brains. Brains.
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Entertainingly, one other species of Aspergillus (Aspergillus terreus) provided us with a useful statin to lower cholesterol. Aspergillus fumigatus produces one toxin of interest for cancer treatment. Candida albicans, the good old fashioned yeast infection known as crotch rot and occasionally athletes foot in immunocompetent individuals. Cryptococcus neoformans, interesting, as it makes phagocytes (immune cells that engulf pathogenic organisms) literally barf up intact yeast (yes folks, it’s really a yeast) and a bit more annoying to get rid of.
Annoyingly, I’m part of that 1% group of the population utterly intolerant of statins at all, my muscles literally begin to dissolve at even a below minimal dosage.
Speaking of Candida infection, got rushed a bit cleaning up after using the toilet, got the itchies, so excuse me while I go retrieve the Holy Hand Grenade of Antioch. Or at least my stock antifungal… Next time, I’m just gonna let that damned phone ring through to voicemail!