The Indian cabinet has told doctors to look out for signs of mucormycosis or “black fungus” in coronavirus patients as hospitals report a surge in cases of the rare but possibly deadly infection.

At the weekend, the state-run Indian Council of Medical Research (ICMR) said doctors treating coronavirus patients, diabetics and those with compromised immune systems should watch for early symptoms including sinus pain or nasal blockage on one side of the face, swelling or numbness, one-sided headache, loosening of teeth and toothache.

The disease, which can lead to blackening or discolouration over the nose, coughing blood, chest pain, blurred or double vision and breathing difficulties is strongly associated with diabetes. And diabetes can in turn be exacerbated by steroids such as dexamethasone, used to treat severe coronavirus.

David Denning, a professor at Britain’s Manchester University and an expert at the Global Action Fund for Fungal Infections (GAFFI) charity, said “there have been cases reported in several other countries – including the UK, U.S., France, Austria, Brazil and Mexico, but the volume is much bigger in India.”

“And one of the reasons is lots and lots of diabetes, and lots of poorly controlled diabetes,” Denning added.

India has not published national data on mucormycosis but has said there is no major outbreak. Media reports have pointed to infections in Maharashtra and its capital Mumbai, and Gujarat.

“It’s not something to panic about, but you have to be aware of when to seek consultation,” said Aparna Mukherjee, a scientist at ICMR.

Even before the coronavirus, mucormycosis was more common in India than in most countries, “partly because of the millions who have diabetes,” said Arunaloke Chakrabarti, head of the Center of Advanced Research in Medical Mycology in the Indian city of Chandigarh and an adviser to GAFFI.

He noted that serious cases might require specific antifungal therapy and multiple operations.