MUMBAI : The Mumbai civic body has started the second phase of sero-surveillance study in the city from Monday to assess the spread of COVID-19 and how many people have developed antibodies against the disease.The survey will cover F-North (Dadar, Matunga and Dharavi), M-West (Deonar and Govandi) and R-North (Dahisar) wards, where a similar study was conducted last month, a Brihanmumbai Municipal Corporation (BMC) official said.The study will provide information about the spread of the infection and also throw light on herd immunity, he said."The sero-surveillance study will give an insight into the spread of COVID-19 and development of antibodies.