36.3% of samples have antibodies: BMC’s sero survey

MUMBAI: The third sero surveillance conducted by Brihanmumbai Municipal Corporation (BMC) in March revealed an overall 36.3% seropositivity in the city, registering an uptick of seropositivity among residents of non-slum areas and a decline in residents of the city’s densely populated slums.

Among the 10,197 samples collected in March, the third serological survey found that 41.6% of the residents of slums had been exposed to the virus while 28.5% of people living in nonslum areas like high rises, chawls and other residential areas, had been exposed to the coronavirus.

A serological survey indicates a population-level prevalence of antibodies against Sar-CoV-2, the virus causing the Covid-19 pandemic. It indicates that a person has been exposed to the virus and has recovered from it, but it does not detect the level of antibodies in the person.

Mumbai, which recorded 5867 new Covid-19 cases on Saturday night taking the total to 622,146 persons infected with Covid-19, conducted 838,500 tests in March. The total number of cases registered by March end was 385,661 with a case fatality rate of 3%. The first sero surveillance was conducted in the city in July 2020 and the second was conducted a month later, in August. In the first survey, 57% of samples collected from population residing in slums were seropositive, while in the second survey, 45% were seropositive. In contrast, 16% of samples collected from residents of nonslum areas showed sero positivity in the first survey, which increased to 18% in the second survey.

“It is clear that the percentage of sero positivity in slum areas is decreasing and in non-slum areas the sero positivity is increasing,” the BMC issued a statement on Saturday.

PRAFUL GANGURDE / HT Health workers take a Covid-19 casualty to a cemetery in Thane on Saturday.