While the city is on the alert for a possible second wave of COVID-19 because of migrants returning, 80 per cent of the caseload is still from high-rises. During the contact tracing of such patients, officials say, most were said to be part of gatherings at home.

As slums had emerged as COVID hotspots in the early days of the pandemic, the corporation dealt with it by creating containment zones, with over 500 big slum areas having been sealed. In June, the virus shifted to buildings and most of the cases have continued to come from there.