Will climate change cause more fungal disease outbreaks?

As the COVID-19 pandemic demonstrated, any disruption to the delicate balance of nature has a ripple effect, inevitably reaching us. While common fungal infections like ringworm and yeast can be managed, more dangerous and virulent strains lurk in the shadows. In 2020 alone, an estimated 1.7 million people died from fungal infections. It’s a reminder of the potential threat fungi pose when left unchecked. With climate change accelerating and reshaping our planet, the big question remains: will we see more deadly fungal diseases emerge, propelled by the changing environment? The University of Manchester’s Norman van Rhijn explains more…

Norman - Fungi are a vast kingdom of different species, so they really are all around us. They have their own niches, their little homes where they like to live, but obviously, when the world is changing, some places become hotter, some places become wetter or drier, and the fungi will adapt to that accordingly. So they will move into new spaces, they will evolve, and that's what we're likely to see in the future.

Chris - What are you most worried about in that respect? When one considers these sorts of changes in the future, there must be some things that you use as your poster child for this happening, but also things that you say, this is a really big concern if this happens.

Norman - Well, we do a bit of research on a yeast called Candida auris. We didn't know it before 2009, but since then it has spread across the world and caused these life-threatening infections and outbreaks that we've really not seen before. And we think this is the first example of a fungal species that came to be because of climate change.

It's a new species; it's evolved with climate change and is now causing these infections. So my fear is that something like this will happen again, or even worse, we get a fungus that can infect everyone. Luckily, so far, we tend not to see that.

So Candida auris infects people who are already in intensive care, but they are really hard to treat. So yes, a lot of worries over the next 50 years or so.

Chris - What's the mechanism then? Because you're saying that is really the first documented example of a climate change-driven emergence. Why and how?

Norman - We have only a few published cases of where this yeast can be found in the environment, but we've not really pinpointed it as a field. So that's what we're trying to do. And then the next thing we're trying to understand is what traits it has evolved, and why it can infect.

There are some indications. It forms these great biofilms that stick to surfaces and can stay there for long periods of time. It can withstand high temperatures — higher than body temperature.

It can cope with stress really well. It grows rapidly. So these are the things we're looking at.
But so far, we've not pinpointed one particular niche or factor that is driving these infections.

Chris - Have you pinpointed any areas of the world that are likely to be particularly challenged or challenging in this respect? Because we know there are going to be some areas where climate change impacts are greatest, either because the human impact is greatest, the environmental impact is greatest, or both. So are there some hotspots that are likely, therefore, to translate into big changes in what fungi do?

Norman - I think, unfortunately, every part of the world is going to be affected in a different way. And there will be fungi that take that opportunity. I think we already see that fungal infections are a really big problem on the African continent, where we have lots of people still with tuberculosis or HIV, and these are risk factors for severe fungal infections.

And because the antifungals that work relatively well are expensive or not even available in those countries, that is where we see the highest rates of death. So I think if I have to focus on one particular area, it's going to be that. But we're going to get other problems in Europe and North America as we see more people going into intensive care or being severely immunocompromised.

These fungi are great opportunists — if they see a way to consume you as organic matter, they will.
Chris - Pleasant thought. And in terms of the threat that this poses to the environment — because when you've got an infection that's in humans, it's easier to control, because you can control what humans do and you can medicate humans and so on. But when it's an environmental threat and it's got the whole of nature to play with, it's much, much harder, presumably.

Norman - It really is. So thinking about things that infect animals — it's really difficult to treat. There was a fungal infection which was rampant across amphibians, and we saw rapid decline in these animals.

There's an example of outbreaks among these parrots — kakapo species that are already close to extinction — and it wiped out about 10% of the entire population. But also, if we think about plants and crops — massive crop loss — and trying to rein in fungal infections is incredibly difficult. And that is why our farmers are having to use tonnes and tonnes of fungicides each year to save their crops.

Chris - But are they paradoxically accelerating the problem by doing that? So as we effectively pour more petrol on the fire to control it, we're actually driving the evolution of these fungi and possibly intensifying things?

Norman - Partially, but there is a group of fungi that are the main drivers of plant infections, and only a very limited group are able to cause both plant and human infections. So they're still a relatively separate problem. But there are some examples where we have these cross-kingdom fungal species, and actually what we already see is that they are exposed to these chemicals in fields — and that's exactly where they start to evolve resistance to the antifungals we use in the clinic.

So we've got this dual problem of trying to fight both nature and evolution.

Chris - We've dwelled quite heavily on the bad news. Hopefully you've got some good news for us in terms of what we might be able to do about this in order to swerve around some of these things that you say are the rocks in the path ahead.

Norman - Luckily, it always starts with awareness. And I think if we compare where the field is now to 20 years ago, there's a lot more awareness and cross-talk between these fields of research. So we now see that clinicians are starting to speak to farmers and to policymakers so we can actually start doing something about it.

On top of that, we've got some great novel molecules that are hopefully going to come out within the next few years in agriculture, and also to treat human infections. So I've got great hope that there will be something out there that we can use to treat these infections.