A new superbug threat spreading across the world comes from microscopic fungal spores. Fungus in the genus Coccidioides are on a World Health Organisation list of 19 fungal species deemed top priorities for the development of new drugs. They can give rise to coccidioidomycosis, which is also known as valley fever.
These microscopic organisms are found in desert soil in the southwestern US, Mexico and parts of Central and South America. Valley fever in the UK is mainly due to infected people entering the country. Incidents in Britain are relatively small, according to a 2021 National Institutes of Health study
Coccidioides spores can be inside or on the body. They can be found in the air and in dirt. But while there are hundreds of antibiotics to treat bacterial superbugs, there are only about 17 antifungal drugs in circulation, according to the US Centers of Disease Control and Prevention. A reason for this is that it is harder to make drugs which kill fungus without harming people.
Dr Neil Clancy, an infectious disease specialist at the University of Pittsburgh, told CNN: “Genetically, fungi are more closely related to humans than they are to bacteria.
“If you’re trying to make an antifungal drug, you’ve got to come up with targets that won’t harm genes and proteins humans have.”
He added that at the moment, the drug in use, which kills fungus the best, cross-reacts with human kidney cells, so people can end up with kidney failure.
Anti-fungal drugs can also lead to pancreatitis, liver damage, severe allergic reactions and impotence.
Those who are most vulnerable to invasive fungal infections are people whose immune systems have been weakened, such as those with HIV/Aids or who have had chemotherapy.
Infections in otherwise healthy individuals are usually dealt with using current antifungal treatment, but some people can struggle to recover from coccidioidomycosis, or cocci, the disease caused by the fungi.
Common symptoms of coccidioidomycosis include fever, headache, a dry cough, shortness of breath, chest pain, myalgia and arthralgia. It may be accompanied by a rash, according to the BMJ.
At the top of the WHO’s list of four fungal parasites most critical for research and new drug development is Cryptococcus neoformans, which causes a potentially deadly form of meningitis.
CNN reports that the death rate from an infection with Cryptococcus neoformans is extremely high at up to 61%, especially in patients with HIV infections.
Aspergillus fumigatus, a mould which damages the lungs and can spread to other parts of the body, appears second on the list.
Candida auris comes third on the WHO list. This microbe was already resistant to all four classes of fungicidal treatment when it appeared in the US in 2013.
Candida albicans, a cousin of Candida auris, is a common yeast which lives in small amounts on the skin, in the mouth, throat, intestines and vagina. This one is fourth on the WHO’s list.
In a healthy microbiome, it lives peacefully in the body and may play a role in boosting immunity, but when that balance is disrupted by antibiotics or an immunosuppressant it can cause yeast infections or lead to antimicrobial-resistant invasive candidiasis.