They sound like something from a dystopian disaster film: invisible clouds of fungal spores sweeping across continents on the wind, infiltrating lungs and spreading disease.
What is a fungus storm?
You might be imagining an irate toadstool, but the truth is less strange but more insidiously deadly. Essentially, a fungus storm is when strong winds pick up and carry microscopic spores from fungi, as well as particulate matter and other micro-organisms, often over huge distances.
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There is evidence that climate change is not only causing these sorts of extreme weather events to become more frequent but also allowing certain groups of fungi to become more resilient and expand into new areas. These are mostly fungi that you never see and whose spores are also invisible to the human eye – but which can affect our health.
Are they a problem, then?
Yes, definitely. There’s a couple of closely related, soil-living fungi, Coccidioides immitis and C. posadasii in case you badly wanted to know their names, that are responsible for an illness called valley fever in the USA. One study found there was a strong correlation between the growing frequency of windblown dust storms in the country – they rose by 240 per cent in recent decades – with the increased incidence of valley fever, which soared by 800 per cent between 2000 and 2011.
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Is valley fever bad?
It certainly can be. About 10,000 cases are reported every year, with 70 per cent of them occurring in Arizona, but 60 per cent of people exposed to the Coccidioides spores do not get ill. But for those who do develop symptoms, these can be extreme tiredness, a cough, fever, headaches, night sweats and muscles aches. Up to one in 10 people who get valley fever will sustain long-term damage to their lungs, and for about 1 per cent, the infection can spread to their brain and spinal cord and other parts of their bodies. Most cases are reported from the states of Arizona and California, and it’s thought that about 160 people die each year from it.
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What can happen to people who develop valley fever?
A British jeweller on a month-long business trip to a gem fair in Tucson, Arizona contracted valley fever and ended up having a part of his lung removed, along with a lump of Coccidioides the size of a golf ball. The BBC reported that he avoids the underground and buses to minimise his chances of picking up other infections, that stairs make him out of breath and he gets aches and pains all over his body.
He also overheats and has long-term fatigue. But experts say we need to put the illness into perspective – if you spend a year in an area where Coccidioides is common, then you have a 3 per cent chance of getting infected and a 1 per cent chance of getting sick. Farm and construction workers are most at risk.
5 Why is it called valley fever?
When we first became aware of it at the end of the 19th century, the San Joaquin Valley – a large area of Central California and one of the principal locations in which John Steinbeck’s famous novel The Grapes of Wrath is set – quickly became notorious for harbouring numerous cases. In Ventura County, just north of Los Angeles, there was a sudden spike in infections after an earthquake. And though anti-fungal drugs can help to alleviate symptoms, there’s no cure.
Are other fungus species dangerous, too?
Yes, there’s three species in the Aspergillus genus, a fungus that we would normally be called a mould and exists to break down dead material, that are spread by dust storms and there’s research suggesting infections in Europe will rise as a result of increasing extreme weather events and humidity caused by climate change. In 2022, the World Health Organisation added Aspergillus to its priority list of emerging threats. As with valley fever, most people can come into contact with it and not become ill, but for those that do, it’s a familiar medley of symptoms such as a cough, shortness of breath, headaches, fatigue and, in some cases, coughing up blood. People with weakened immune systems are most at risk.
Are airborne fungal spores only found in dry environments?
No. This study identified spores of both Ascomycota – also known as sac fungi – and Basidiomycota (a group which includes well known edible fungi such as boletes and puffballs) present in air masses over a wide area of northern hemisphere oceans from the Pacific Northwest to the Arctic. These fungal spores can help water droplets and ice form within clouds, thus impacting rain and snow precipitation.
Is there a cost associated with fungus storms?
We certainly know that dust storms cost an eye-watering amount of money (as well as potentially making your eyes water). For example, BBC Science Focus reports that sand and dust storms cost North Africa and the Middle East more than £100 billion a year and that in 2017, wind erosion and dust cost the US economy about the same amount (and that it had increased four-fold in 20 years). Much of this is damage to property and other infrastructure, but the health impacts from fungal spores will also have a price tag associated with them.
Any other fungal spores I should be worried about?
Unfortunately, yes. There’s one called histoplasmosis, an infection caused by a fungus found in bird and bat droppings. Histoplasmosis is common in the mid-western states of the USA, but is also found in all the other continents apart from Antarctica.
As with other fungal infections, many people who contract it will not suffer any symptoms, while others will get the usual medley of fever, headaches, coughs and tiredness. Immune-compromised people can however experience much more serious impacts that include acute respiratory symptoms and inflammation of the tissues around the heart.
Any others?
Yes, there’s another one called blastomycosis, which is caused by fungi found in moist soils in wooded areas and along waterways. It’s very rare – in the state of Minnesota, for example, an average of about 40 people and 120 pets are diagnosed with the condition (though these numbers do appear to be increasing). You catch it by breathing in the spores from soil where the fungus lives, so it seems unlikely that this one is linked to fungal storms. About half of all infections cause no symptoms or very mild ones.
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