Relatives embrace next to the body of a person who died of covid-19, at a crematorium in New Delhi on Tuesday. (Money Sharma/AFP/Getty Images)

As coronavirus cases and deaths soared in India recently, doctors began to notice another disturbing trend. Some covid-19 patients who had been released from hospitals were coming back with different symptoms, including sinus pain, blurred vision, black and bloody nasal discharge and a dark discoloration around the nose.

The culprit was a deadly fungal infection called mucormycosis that physicians say is increasingly preying on people with immune systems weakened by covid-19 and the steroids used to treat it.