BMC to begin second phase of sero-surveillance on August 10

The city crossed the 5-lakh mark for testing Covid-19 samples on Wednesday, recording the single-day highest of 11,643 tests conducted in 24 hours. The total number

The city crossed the 5-lakh mark for testing Covid-19 samples on Wednesday, recording the single-day highest of 11,643 tests conducted in 24 hours. The total number of tests conducted so far is 5.05 lakh.

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To expand the scope of its testing, the Brihanmumbai Municipal Corporation (BMC) will begin the second phase of its sero surveillance survey from August 10. The survey will be carried out in R-North, M-West and F-North wards, to help the civic body ascertain the spread of Covid-19 in these areas.

On Wednesday, Mumbai recorded 1,109 fresh cases and 60 new deaths, taking the city’s case tally to 111,991 and toll to 6,247. The number of discharged patients in Mumbai was 85,327 with a recovery rate of 76.11% and active cases stood at 20,123. The fatality rate was 5.57% and doubling rate is 72 days. One hot spot that has shown signs of drastic improvement – Dharavi – recorded only two new cases on Wednesday, bringing the area’s case count to 2,545 of which 2,212 have been discharged.

Over the past five days, the number of tests conducted in Mumbai daily has gone up due to the use of rapid antigen kits. Of the daily testing tally, approximately 30-35% are conducted using rapid antigen kits, said BMC officials. By May 6, the city had conducted more than 1 lakh tests. The 2-lakh mark was crossed on June 1 and on June 24, the 3-lakh mark was crossed in the testing tally. On July 14, the city had carried out more than 4 lakh tests and on Wednesday, BMC said a total of 5.05 lakh tests have been conducted.

BMC has also sought opinion from state government authorities on how to undertake a sero-surveillance survey on a population larger than the sample used in the first phase. On July 3, BMC in collaboration with Niti Aayog and Tata Institute of Fundamental Research, started a sero-surveillance survey in three wards in the city to identify recovered individuals and estimate the spread of Covid-19. In a sero survey, a sample set of individuals undergo blood tests to detect the presence of immunoglobulin-G (IgG) antibodies, which are produced by the body’s immune system upon exposure to a virus.

On Tuesday, BMC released findings from the sero survey conducted by the civic body as part of a national study to understand the spread of Covid-19. In Mumbai, the survey of 6,936 people from R-North, M-West and F-North wards found 57% from slums and 16% from other residential areas had the antibodies, suggesting they had been exposed to Covid-19 and recovered. The survey also revealed that 60% of those diagnosed with Covid-19 have been male and more women recovered after being exposed to the virus.

The civic body plans to undertake a second phase of the study in the same wards, covering neighbourhoods like Dahisar, Borivli, Matunga, Dadar, Wadala and Chembur. Suresh Kakani, additional municipal commissioner, said, “We will start the second phase in the same area from August 10. The areas will be the same to help us understand the community in those specific areas better. However, the samples will not necessarily be from the same individuals. But it will be from the same area, considering we have to gauge the antibodies in the surrounding community.”

Kakani added, “Whether to go ahead and conduct sero survey on the larger population can only be ascertained once the results for the second phase are out. By mid-September, we anticipate that the results for the second phase will be out.”

Officials said the civic body is exploring how a sero survey may be conducted on a larger population and whether the help of private laboratories would be needed in such a survey.

A BMC official said, “We are also carrying out discussions with the state health department on the same. We also have to consider the reluctance by many to give samples. The problem with private laboratories will be consent. We should have consent of the individuals who come for their blood check-up on whether we can use their body to test antibodies or not. This process becomes difficult, and hence we will have to wait until the results for the second phase are out to better understand the modalities for the third phase.”

After the first phase of the sero survey, BMC officials said the results indicate populations in slum areas have developed antibodies. Kakani said, “Our focus is clear that high-rises and housing societies are going to be crucial as slums areas seem to have developed antibodies.”