The state-run Indian Council of Medical Research (ICMR) said at the weekend that doctors treating COVID-19 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, one-sided headache, swelling or numbness, toothache and loosening of teeth.

The disease, which can lead to blackening or discolouration over the nose, blurred or double vision, chest pain, breathing difficulties and coughing blood, is strongly linked to diabetes. And diabetes can in turn be exacerbated by steroids such as dexamethasone, used to treat severe COVID-19.