The Brihanmumbai Municipal Corporation (BMC) on Tuesday announced the results of its first serological surveillance in the city.

The sero-survey study, carried out in three wards of Mumbai, found that 57 per cent of the people tested who were exposed to the novel coronavirus were from slums, and 16 per cent from residential housing societies.

The prevalence in women was found to be marginally higher than in men. The results of the sero-survey also suggested that a higher proportion of the overall infections were asymptomatic infections.

“Taking together the current prevalence (estimated here) and records from BMC on reported deaths, the infection fatality rate (IFR) is likely to be very low (0.05-0.10 per cent). Among others, this could be attributed to effective containment efforts and active measures to isolate symptomatic cases by the Municipal Corporation of Greater Mumbai (MCGM),” the municipal authority said in an official release.

“These results will be valuable to learn more about herd immunity. Although it is still unclear what level of prevalence leads to herd immunity, findings indicate that at least in slums this could be attained sooner than later if the immunity exists and persists in a significant proportion of the population,” it said.

BMC further suggested that proper measures related to hygiene and sanitation, including measures such as social distancing, are proving to be effective in controlling infections.

The survey was conducted in Chembur, Matunga and Dahisar areas for 12-14 days in the first half of July. In the first round, 6,936 samples were collected from the general population in slum and non-slum areas.

The survey was jointly commissioned by NITI Aayog, MCGM and Tata Institute of Fundamental Research.

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