A serological surveillance for SARS-CoV2 infection in three slum and non-slum areas of Mumbai, has among other things estimated sero-prevalence of 57 per cent in slums and 16 per cent in non-slums and suggested that asymptomatic infections “are likely to be a high proportion of all infections”.
The serological surveillance, commissioned jointly by NITI Aayog, Birhanmumbai Municipal Corporation and Tata Institute of Social Sciences (TIFR), has said that higher prevalence in slums could possibly be due to population density and shared common facilities like toilet and water points. “Taking togerher the cureent prevalence 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 BMC,” a statement put by the BMC said. The agencies that undertook surveillance collected 6936 samples in the first round from three BMC wards (R-North,M-West and F-North).
“Anti-SARS-CoV2 IgG antibodies were detected using Chemiluminescence assay (CLIA) by Abott. The study period ranged from 12 to 14 in the first half of July 20202. The participants recruited comprised 100 per cent of target numbers in slums and 70 per cent in non-slums. “The results will be valuable to learn more about herd immunity. Although it is unclear what level of prevalence leads to 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,” the statement said.
“The ongoing study will provide information on the presence of neutralizing antibodies, risk factors on SARS-CoV2 infection. Planned repeat surveys will provide information about infection spread in both slums and non-slums and could inform about the herd immunity,” the statement added.