Let me introduce you to something truly horrifying – the fungus that turns its victims into zombies.
Its spores enter the body. The fungus then grows and begins to hijack the mind of its host until it loses control and is compelled to climb to higher ground.
The parasitic fungus devours its victim from the inside, extracting every last nutrient, as it prepares for its big finale.
Then – in a scene more disturbing than the scariest horror film – a tendril of death erupts from the head. This fruiting body of the fungus showers spores on everything around it – dooming others to the same zombie fate.
It sounds like a work of fiction. But the kingdom of fungi – distinct from plants and animals – ranges from edible mushrooms to nightmare-fuel parasites.
Species of parasitic Cordyceps and Ophiocordyceps fungi are very real. Here, on the BBC’s Planet Earth series, Sir David Attenborough watches as one takes control of an ant:
That clip of zombie ants inspired “The Last of Us” – possibly the best video game I’ve ever played, and now a hit TV series which follows the same plot.
In both the game and on TV, Cordyceps makes the leap from preying on its usual insect victims, to infecting humans. The resulting pandemic leads to the collapse of society.
But in the real world, is a Cordyceps pandemic – or one caused by another fungus – ever likely to happen?
“I think we underestimate fungal infections at our peril,” Dr Neil Stone, leading fungal expert at the Hospital for Tropical Diseases in London, tells me.
“We’ve already done that for too long and we are completely unprepared for dealing with a fungal pandemic.”
At the end of October last year, the World Health Organization (WHO) issued its first list of life-threatening fungi.
There are some nasty bugs on there, but you’ll be relieved to know that zombifying-Cordyceps do not feature.
Dr Charissa de Bekker, a microbiologist at Utrecht University, has studied how Cordyceps creates zombified ants and says she cannot see the same ever happening in people.
“Our body temperature is simply too high for most fungi to nicely settle and grow – and this is the same for this Cordyceps.
“Their nervous system is simpler than ours, so it would definitely be easier to hijack the brain of an insect versus our brain, also their immune systems are very different from ours.”
Most species of parasitic Cordyceps have evolved over millions of years to specialise in infecting just one insect species. Most do not jump from one insect to another.
“For this fungus to be able to jump from an insect to us and cause an infection is a very big leap,” says Dr de Bekker.