Weakened lungs and immune systems make people increasingly vulnerable, warn scientists.

A rash of cases of a rare “black fungus” infection affecting thousands of critically ill Covid patients in India caused alarm last month. Now scientists are warning that other dangerous or even deadly fungal infections have spawned in critically ill coronavirus patients globally, including in the UK.

Fungi are ubiquitous – in soil, water, air, faeces and human skin. Usually, people’s elaborate, adaptive immune systems are enough of a repellent but when that shield is weakened by disease, congenital conditions or age, they are far more vulnerable to microscopic assailants.

When Covid-19 emerged, doctors found that the best tools in their arsenal to fight the virus were steroids, which happen to be immunosuppressants. Wary of secondary bacterial infections in intensive care units, doctors often gave coronavirus patients broad-spectrum antibiotics as a precaution.

“It’s an unfortunate perfect storm for these organisms, and we’re seeing it,” said Dr Tom Chiller, the chief of the Mycotic Diseases Branch at the US-based Centers for Disease Control and Prevention (CDC).

Even before the pandemic, rates of the rare and lethal “black fungus” mucormycosis infection in India were estimated to be about 70 times higher than in the rest of the world. With Covid, a fresh epidemic germinated, driven in part by liberal steroid use in hospitals and a high proportion of susceptible patients with uncontrolled diabetes.

Scientists now say concerning reports of other fungal infections, caused by pathogens including Aspergillus and Candida auris, have emerged in hospitalised Covid patients. In particular, the common fungal infection aspergillosis, often seen in combination with the flu, has been observed in critically ill Covid patients globally, from the US to the UK, France, Pakistan and India.