More than 4,300 people have died of the deadly "black fungus" in India in a growing epidemic that mainly affects Covid-19 patients.
It's thought that this drop in immunity could be triggering cases of mucormycosis in diabetics or severely immunocompromised individuals, such as cancer patients or people with HIV/Aids.
Dr Raghuraj Hegde, a Bangalore-based eye surgeon who has treated a number of mucormycosis patients, told the BBC that there had been "massive undercounting of both cases and deaths" from the disease.
Doctors said that many patients had died from the disease even before reaching a hospital and a number of treated and recovered patients appeared to be suffering from a relapse.
"We are seeing patients who were treated aggressively for the disease and discharged from hospitals returning with a recurrent infection which is manifesting in wider spread of the disease in the eye or brain," Dr Akshay Nair, a Mumbai-based eye surgeon, told the BBC.