The Last Of Us: The science behind the real 'zombie' fungus - and is it an actual threat?

The threat of such an emergency is posed at the outset of the hit TV series, The Last Of Us, which begins in the 1960s with a bleak speech by an epidemiologist on the danger of fungi.

"If the world were to get slightly warmer, then there is reason to evolve," warns a prescient John Hannah, referencing their potential to infect and overpower a person's mind.

"Candida, ergot, cordyceps, aspergillus: any one of them could be capable of burrowing into our brains and taking control of not millions of us, but billions."

The show takes this idea and runs with it, jumping forward 40 years to when a mass cordyceps outbreak leads to a devastating pandemic which transforms people into blood-thirsty abominations.

An extreme outcome with plenty of artistic licence taken - but is it entirely without scientific basis?

Do fungi really threaten humans?

"There are numerous fungi infecting the brains of human beings all over the planet, often with devastating outcomes," says Professor Elaine Bignell, a world leader in the field of human fungal pathogen research.

"A number of fungal species are quite prominent pathogens and kill hundreds of thousands of people every year - it's just that the public is not well aware of this."

The Last Of Us viewers may have noted that a few of the dangers identified by its fictional epidemiologist featured last year on a list of health-threatening fungi by the World Health Organisation (WHO).

Among the fungi deemed most high-risk was Aspergillus fumigatus, a common mould that is widespread in the environment in homes and outdoors, which can cause "chronic and acute lung disease" and can be deadly.

Candida species, which are behind complaints like thrush and skin rashes, are also one of the leading causes of bloodstream infection in intensive care patients.

Cryptococcosis neoformans - which infects the lungs and brain, causing pneumonia and meningitis in immunosuppressed patients - also made the list. It kills more than 100,000 people a year in sub-Saharan Africa.

"One thing that killer fungi do have in common is that they are able to grow at human body temperature, and that's unusual for a fungus," Prof Bignell tells Sky News.

"Most fungi in the environment are suited to growing in more temperate conditions, and it places quite a strain on any microorganism to counteract an immune response in a human body and cope with the high temperature."

Cordyceps was not on the threat list - but it is absolutely real.

The parasitic fungus infects and takes over the mind of insects, as it does to humans in The Last Of Us.

"There are about 600 species," says Dr Mark Ramsdale, a professor in molecular microbiology at the MRC Centre for Medical Mycology.

"They are predominantly insect pathogens. It's their insect host that they manipulate and change their behaviour. And so from that perspective, there is some basis there."

Found in tropical forests, the fungus penetrates an insect's body via spores, which are released to allow a fungus to reproduce and defend itself.

The fungus then guides its host into more humid locations to help it grow, before feeding on the remains and launching new spores from its corpse.

When it comes to humans, cordyceps is used in treatments and therapeutics - notably Chinese herbal medicines.

"There's a long history of relationships between humans and this particular group," Dr Ramsdale tells Sky News.

"There's no evidence they're causing disease in humans. However, in terms of their insect relationships, they do manipulate their hosts - and several fungi have evolved this capacity over time."

-sky news