The number of positive cases is high in North Chennai, particularly, in Royapuram, Thiru Vi Ka Nagar Tondiarpet, Aynavaram and Pulianthope due to high density of population. To control it, each zone has a team consisting of IAS officer, IPS officer, DRO and medical officer that is working on containment measures. “We are studying the pattern. The cases were not spread across the zone but in a few wards. Even in the wards, it is limited to a few streets.