Fungi are everywhere, and whether you realise it or not – or whether their presence brings human benefit or infection – these microorganisms are a frequent feature of everyday life.
They’re in the kitchen, from the yeast that ferments the beer, bread and wine served at your favourite restaurant, to the mould that will soon appear on the food in your fridge, which you really should have stayed in and eaten instead. Precious Italian white truffle sprinkled on pasta in Piedmont is also a fungus, as is the mushroom that makes up the meat alternatives you buy in the supermarket.
They’re also in your closet, woven into that vegan leather jacket, your Adidas Stan Smith’s, lululemon leggings and even your yoga mat – if the items bought from these brands come from their mycelium or “mylo” ranges, they’re made of fungus.
They’re also of course, in the wild, where these microorganisms play a key role in the forest microbiome and biodiversity, even helping to capture carbon from the atmosphere and sequester it in the soil. A power which many climate biotechs and NGOs are now trying to harness to help tackle the climate crisis.
As such, human co-existence with fungi is, in many ways, harmonious, and more than that, there’s even a myriad of benefits to be bestowed by exploring this relationship further.
But what must not be forgotten, is that much like bacteria, although there are certainly many “good” fungi out there, there are also plenty which are considered “bad.” Most notably – without taking into account the poisonous or hallucinogenic edible varieties – the many fungal pathogens that cause invasive infection and pose a serious threat to global human health.
It’s this hostile framing of fungi that’s currently on your screen – or if it’s not, it should be – in the form of the hit HBO series “The Last of Us,” which depicts the survival of a man and his 14-year-old sidekick in a post-apocalyptic world decimated by a fungal pandemic. In the dystopian world presented, infected victims are disturbingly agile, unduly angry and worst of all, zombie-like – there’s a lot of biting.
The main premise of the show is that a previously harmless fungus known as “cordyceps” has mutated to become a heat-resistant and highly infectious pathogen, as its newly-evolved capabilities allow it to infect humans and wreak havoc.
If you haven’t seen the show, you might wonder what (in this fictional depiction) drove the fungus to evolve in this unprecedented way. The answer is the very non-fictional crisis that the world is currently grappling with every day: climate change.
What’s more, the inspiration for the HBO horror was in fact taken from a very real brain-eating Cordyceps fungus that infects ants. This fungus does not infect humans in reality, but it is widely used in Chinese traditional medicine.
When ants are infected with cordyceps spores, the insects are essentially “hijacked” by the fungus, which is then able to control their behaviour and every move – rendering them “zombie-like” – compelling them to leave their nest in search of fungus-favourable conditions that will allow the microbe to incubate and multiply as the ant slowly dies.
Soon after the ant’s death, a fungal fruiting body blooms from the ant’s head, optimally poised to disperse the newly-formed spores and infect more ants – much like the finger-like fungus that creepily extends from the zombies’ mouths in the show.
We already know that climate change is capable of melting the Arctic ice caps and resurfacing 50,000-year-old time capsules of ancient “zombie viruses,” revealing that what was once frozen dormant, deep within the permafrost could now pose a risk to global health.
But could our warming world also hold the potential to affect the many fungal varieties that we currently co-exist on Earth with? Or is this…
Just another zombie show?
Mild fungal infections are not uncommon. In fact, millions of people regularly suffer the irritating, but non-life-threatening symptoms of fungal skin infections such as athlete’s foot, dandruff, thrush or ringworm.
But for individuals that are immunocompromised in some way, fungal pathogens can be deadly, and the incidence and geographic range of such invasive fungal infections are on the rise.
Despite the lack of global awareness and resources directed to tackle these devastating outbreaks, fungi are now responsible for 300 million infections and 1.5 million deaths each year.
To address both the escalation in risk and lack of awareness, in October last year, the World Health Organisation (WHO) published a report cataloguing a “fungal priority pathogens list” (FPPL) – a list of 19 fungal organisms that pose the greatest threat to global public health.
Fungal pathogens can cause illnesses and death.
They are becoming increasingly common and resistant to treatment.
Yet, too little is known about them.
— World Health Organization (WHO) (@WHO) October 25, 2022
“Fungal pathogens are a major threat to public health as they are becoming increasingly common and resistant to treatment,” stated WHO.
The report outlines how common fungal infections – such as oral and vaginal thrush caused by candida albicans – are becoming increasingly resistant to traditional antifungal treatments. WHO also highlights the growing risk that these relatively harmless microbes may soon become capable of causing more dangerous and invasive forms of infection.
“Emerging from the shadows of the bacterial antimicrobial resistance pandemic, fungal infections are growing, and are ever more resistant to treatments, becoming a public health concern worldwide,” said WHO Assistant Director-General, Dr Hanan Balkhy.
📢The WHO fungal priority pathogens list as a game-changer
As fungal diseases are on the rise globally, Fisher & Denning discuss the WHO fungal priority pathogens list and call for improved research, surveillance and public health interventions https://t.co/dhfRugzT16
— Nature Reviews Microbiology (@NatureRevMicro) February 6, 2023
The authors of the review stressed the critical importance of WHO’s new fungal warning list, stating an urgent global necessity to better address the diagnosis and treatment of fungal outbreaks across the world.
The WHO report stated: “Emerging evidence indicates that the incidence and geographic range of fungal diseases are both expanding worldwide due to global warming and the increase of international travel and trade.”
To clarify, we’re not expecting zombies to plague the streets any time soon, but parallels could possibly be drawn between the themes presented in “The Last of Us” and the emerging threat of fungal pathogens on the global population.
Is the show therefore perhaps…
A possible metaphorical glimpse of the future?
We asked Professor David Denning, one of the Nature paper’s authors, Professor of Infectious Diseases in Global Health at Manchester University, and Founder of the National Aspergillosis Centre and Global Action for Fungal Infections (GAFFI), a few questions about how realistic the fungal threat depicted in the show really is.
We started off by asking Prof. Denning to what extent he expects fungal pathogens to acquire heat resistance as they evolve under the environmental pressures of climate change. He responded by telling Impakter that “Fungi are very adaptable.”
In fact, “Candida auris may well have emerged because of global climate changes,” Denning told us.
We also asked Prof. Denning whether he thought it was possible that the incidence of fungal outbreaks could escalate to pandemic levels, similar to the scenarios seen in “The Last of Us” (minus the zombie element of course). He told us that “cases of fungal disease are already grossly under-diagnosed. So they appear rare, when in actuality they are uncommon, but not rare.”
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“We already see hospital outbreaks all over the world, some related to poor hospital hygiene and infection control practice, some related to hospital construction, some related to patient-to-patient transmission… So major outbreaks are possible, especially in vulnerable patients,” said Denning.
When asked whether he expects the threat posed by fungi to increase as the climate crisis worsens, Denning responded, “Yes,” but “to what extent is difficult to forecast.”
He also highlighted the increasing environmental risk posed by fungi, stating that “90% of plant diseases are fungal, with significant losses in food crops and also trees,” listing bananas, frogs, and entire forests as being at risk from fungal-related diseases, death or even extinction.
Denning’s comments highlight the central message of both the WHO report and his own nature paper: Not enough global attention is being focused on the rising incidence of fungal infections.
In fact, many cases go under the radar, concealing the reality of the threat these microbes pose to humanity – a threat which is only expected to intensify as fungal organisms continue to evolve in line with rising temperatures.
Therefore, an immediate global-scale response is required to address the underestimated epidemic of newly-invasive fungal pathogens, lest we risk jeopardising the present and future health of the planet.
Climate change and zombies
What we absolutely should not conclude from the parallel drawn between the flesh-eating scenes in “The Last of Us” and the closer-to-home threat of global warming-induced fungal mutation, is that climate change is in any way likely to cause an outbreak of zombies.
So stop doomsday prepping right now.
What is real, however, is that as global temperatures rise, the hand of natural selection may be forced to select those microorganisms that are genetically better equipped to withstand warmer temperatures.
As this happens, fungi could evolve to become more heat resistant and ultimately more capable of infecting humans – hosts within which their proteins would previously have been denatured before they were able to cause any harm.
Therefore, though we’re not expecting to deal with the living dead, we should be fully prepared to tackle the emergence of a partly climate-fueled global fungal pandemic.
What does this mean for the future of global health? Well, given that it’s also true that antimicrobial resistance is rising and there’s a severe lack of quality fungal diagnostic tests and treatments at present, urgent action is required to surveil and address the emerging global fungal crisis that seems to be going under the radar.
“Better diagnostics is the key to getting on top of fungal disease,” Denning told Impakter, adding that “we also need to track antifungal resistance better than we are currently doing.”
In the Nature paper Denning co-authored alongside Professor Matthew Fisher, also an expert in pathogenic fungi from the MRC Centre for Global Infectious Disease Analysis, Imperial College, London, the pair highlight the importance of a “One Health” approach to tackling worldwide fungal infections.
They cite the increased use of broad-spectrum fungicides in farming and agriculture as a possible factor that has “potentiated the emergence of newly emerging fungal pathogens,” and urge that the inappropriate use of antimicrobials must be phased-out.
Reinforcing the urgent message of WHO’s fungi red list report, Denning and Fisher also emphasise the need for global and national policy change, wide-scale public health interventions and an international push for investment and innovation in developing higher-quality, and more widely accessible detections and treatments for invasive fungal infections.
“Forewarned is forearmed,” state the authors, also underlining the fact that for every one of the 19 fungal pathogens listed in WHO’s report, “no vaccine is available.”
Just in case you’ve seen “The Last of Us,” and upon reading this article are now acutely concerned about the impending zombie apocalypse, rest assured that no cordyceps are featured on WHO’s list of life-threatening fungi.
But all jokes aside, what should resonate as you read this, is the reality of the unmet public-health issue that is emerging, and that this crisis urgently requires global attention.
Once again we’re reminded that curbing climate change is not only important to protect the environment, but also to protect humans from the hostilities that lie within it.
— Dan Walker (@mrdanwalker) January 18, 2023
Correction: This article has been amended since publication to clarify what WHO stated about global warming and international travel and trade in relation to fungal diseases by adding a quote, and to remove a Tweet.
Editor’s Note: The opinions expressed here by the authors are their own, not those of Impakter.com — In the Featured Photo: Close-up of mushroom toadstools. Featured Photo Credit: Marco Allegretti/Unsplash