New Delhi, April 3 -- Nizamuddin, in the heart of Delhi, is to see health workers from the integrated diseases surveillance programme start going door-to-door as they seek to track and contain cases of Covid-19 in what has emerged the latest and biggest cluster of the coronavirus disease in the country. Cases of Covid-19 have been traced back to a religious congregation of the Tablighi Jamaat at its headquarters in the area, attended, through March, by thousands of the group's members. On Wednesday, the last of the 2,346 people who had been in the building were evacuated; 536 of them were sent to the hospital and 1,810 placed in quarantine....