Will climate change lead to more fungal infections?

Fungi are everywhere. They’re in the air, in the soil and inside our bodies. They’re among the most abundant organisms on the planet – and they can have a significant impact on human health.

Despite this, we know very little about them. The fungal kingdom is largely unexplored by science. Less than 10 percent of an estimated 1.5 to 3.8 million fungi species have been described and only a tiny fraction have had their genetic material (genome) sequenced.

We do know that fungi have an incredible ability to adapt to different environments. This is why the effects of climate change are so important. As the climate changes, fungi are changing too – some are adapting to rising temperatures and spreading to new geographies, including urban areas.

This could have serious consequences for our health.

Currently, over 200 fungal species are known to cause disease in humans – these are called pathogenic fungi. Collectively, these species cause an estimated 2.5 million deaths each year. And a lack of good diagnostics and surveillance means this number could be far larger. Global heating and extreme weather events mean the threat could increase.

But fungi do many amazing things too. They can help us protect the environment, grow food and even develop new medicines. Fungal discovery research could uncover even more benefits.

Fungi play a crucial role in all ecological systems, largely thanks to the symbiotic relationships formed between fungi and plants. It’s estimated that 90 percent of plants worldwide have fungi associated with their roots. In other cases, we’ve harnessed the power of fungi to bring benefits to medicine. 

• Fungi can make plants and soil more resilient. Fungi decompose dead plants and animals, returning nutrients to the soil. The fungus gives the plant water and nutrients in exchange for sugars. By doing this, fungi help plants and soil withstand climate extremes like drought. They can also help plants defend themselves against infections from other fungi and bacteria. As this includes crops, it benefits food security.
• Fungi can capture carbon. Plant-associated fungi store 13 gigatons of carbon dioxide in the soil, equating to a third of yearly global fossil fuel emissions. Some fungi also help trees and forests to absorb more carbon dioxide, while slowing its rate of return to the atmosphere.
• Fungi have incredible benefits for medicine. They’re used to produce many important drugs, including antibiotics like penicillin. Fungi-derived potential drugs for cancer, epilepsy and treatment-resistant depression are in early clinical trials.

Understanding more about fungal biology could lead to incredible scientific discoveries and help us to solve health challenges. Harnessing fungi’s potential could provide innovative solutions for the future, such as developing more sustainable technologies.

But fungi’s adaptability and resilience are also why they can threaten our health.

Fungi’s resilience means they can survive and thrive in places that other organisms can’t — even inside Chernobyl’s nuclear reactors.

Rising global temperatures are causing some fungi to develop the ability to survive at higher temperatures.

Right now, the temperature of the human body is too high for most fungi to survive. But as they adapt to global heating, our body temperatures may no longer work as a defence against infection.

Changes in habitats and weather patterns are also leading fungi to spread to new geographies. This will put new populations at risk. 

A perfect storm of factors is increasing the threat of fungal disease.

• Climate change is helping pathogenic fungi to spread to new places. For example, the Coccidioides fungus lives in hot, dry environments – and as more places experience droughts, there are more places Coccidioides can survive. This fungus causes potentially fatal respiratory infections.
• New fungal pathogens are emerging. Candida auris is considered the first new fungal pathogen to emerge due to climate change. It emerged simultaneously on three continents and was ‘born’ resistant to certain antifungal drugs. Candida auris infects people who are already ill and can cause sepsis and multiple organ failure. Candida auris has spread to healthcare environments, where it can grow on plastics in medical equipment.
• Natural disasters and extreme weather events can trigger fungal disease outbreaks. Wildfire smoke, large storms, floods and heatwaves can spread fungal spores over large distances. Disasters can leave people with skin injuries, displaced into cramped accommodation, and with inadequate sanitation. These factors put people at higher risk of fungal infection from contaminated water or soil.
• The risk of zoonotic fungal diseases is growing. Animals are also vulnerable to fungal infections, and habitat loss increases the risk of illnesses passing from animals to humans.
• Fungal infections are threatening food security. Fungal colonisation of crops can reduce crop yields by a third. And fungi are contaminating food and animal feed, which can lead to illness and death. Farmers spray crops with the same antifungal drugs used to treat infections in humans, which increases antifungal resistance.
• Climate change may help fungi become more drug-resistant. There’s emerging evidence that higher temperatures may help fungi evolve to survive fungicide exposure. As well as aiding the spread of fungal pathogens, climate change may make them more difficult to treat.

While some fungal infections are mild, others are life-threatening. Despite this, healthcare professionals often don’t consider fungal infections when treating patients.

Fungal infections can be hard to recognise, because their symptoms overlap with other common conditions. Healthcare professionals may only realise an infection is fungal when antibacterial drugs don’t work to treat it. Diagnosis is difficult, as there are few effective tests and access is limited.

Even when these infections are diagnosed, they can be very hard to treat.

Currently, there are only four classes of antifungal drugs. Similar drugs are used in both agriculture and medicine, giving fungi more opportunities to develop resistance.

Developing safe antifungal drugs is extremely challenging. This is because fungi share more genetics with humans than with plants. Drugs that harm fungi often also harm us.

Fungal pathogens mainly attack people who are already vulnerable.

This includes elderly people, people with existing illnesses and people whose immune systems are weakened or suppressed. This might be by infection, or by treatments like chemotherapy or organ transplants.

The number of vulnerable people worldwide is growing. People are living longer, including after treatment for serious illnesses, leaving them more susceptible to fungal diseases.

But fungal infections among otherwise healthy people are also growing.

For example, the Covid-19 pandemic saw the spread of Mucormycosis – ‘black fungus’ – in India. This fungus infected recovering Covid-19 patients, attacking body tissues. Severe cases required removal of infected eyes, noses and jawbones. Some infections were deadly.

As climate change spreads pathogenic fungi to new locations, more people worldwide will be at risk.

The communities most at risk from fungal disease are the same as those most vulnerable to the health impacts of climate change. Low- and middle-income countries are most impacted, though fungal pathogens affect everyone.

To tackle the increasing threat of fungal infections, we need:

• new antifungal drugs to protect ourselves and our food supplies
• better regulation around fungicide use, to minimise antifungal resistance
• more monitoring and surveillance to understand the scale of the challenge

We also must harness fungi’s incredible potential to benefit humans and ecosystems. Understanding more about fungi’s biology could help us to develop new medicines, make agriculture more sustainable, and improve carbon capture in the journey to net zero.

To do this, we need more research, funding and awareness.

This year, Wellcome is investing over £50 million in fungal research across our Discovery Research, Climate and Health and Infectious Disease programmes.

We’re already supporting many fungi projects, including working to sequence the genome of every fungi species on Earth and understanding how fungi adapt to global heating.

The fungal kingdom is still underexplored by science. More research is vital for human health everywhere.