What causes the disease?
The fungal strain responsible for the apocalypse in the show is called Cordyceps, and ‘The Last of Us’ proposes that a mutated version of this fungus has infected people globally. It initially spreads through fungi-infested flour and grain but is later spread from person to person through bites and the inhalation of spores.
Ophiocordyceps unilateralis is the fungus the show is based on and is aptly named the ‘zombie-ant’ fungi. This fungus spreads via spores in the air, which find an ant host to colonise and take over. O. unilateralis eventually spreads through the whole body, causing behavioural changes by the release of chemical signals. This makes the ant move to higher and hotter ground, so that when it releases its spores, they can spread further and infect more ants.
Whilst this fungus doesn’t make ants try to attack and eat each other, it does force the ant to enact a ‘death grip’. Once the ant has found a suitable leaf, it attaches its mandibles to the underside of the leaf, and awaits death. The fungus uses the ant’s body for nutrients and to produce a fruiting body, which is full of spores, ready to burst and spread the disease to other colonies.
How does this behaviour compare to ‘The Last of Us’ zombies?
They’re fast, they’re strong, they’re terrifying, and they’re not prepared to wait for death to spread their spores. These zombies’ sole purpose is to propagate and spread the fungi to as many as possible, just like their real-life counterparts. However, their methods involve more biting and chasing down potential new hosts, rather than passively spreading spores in the air.
The disease is shown to spread pretty fast, with a bite resulting in infection within hours. There are indeed some fungal strains that spread through punctures in the skin, though these usually occur in hospitals due to catheter insertions and not due to human bites.
So, how likely is O. unilateralis to cause a real-life zombie apocalypse?
Ophiocordyceps unilateralis has co-evolved with its host, the carpenter ant, for millions of years. To make the jump to infect humans, a multitude of random mutations would have to happen in quick succession and that just isn’t likely. In fact, the fungus hasn’t even made the jump to any other animal apart from ants, so it seems we’re pretty safe from this fungus for now. The Cordyceps fungi are currently used for medicinal purposes, and some people are even encouraged to consume the fungi for health benefits.
The first episode of season 1 does mention some alarming factors that are indeed contributing to a dangerous rise in fungal infections. Climate change, lack of new antifungal drugs, and antifungal drug resistance are all helping other fungal strains to achieve pandemic status, and they certainly pose a threat to our future health.
Fungal strains like Aspergillus fumigatus are posing significant issues to human health, but fortunately, it is currently restricted to those who have a weaker immune system, and cannot cause a global pandemic yet. There is promising research into new classes of antifungal drugs, and into how we can fight climate change, but we must be vigilant to emerging fungal strains that could cause widespread infection.
‘The Last of Us’ zombies aren’t likely to come to life, but another pandemic, this time fungal, could still be on the horizon.
