The Brihanmumbai Municipal Corporation (BMC) will begin the second round of serological surveillance, or sero survey, by the end of this week. The survey will be conducted in M (West), F (North) and R (North) wards, which are the same wards where the first sero survey was carried out in July. Researchers said the surveying the same wards would allow them to compare data to better understand the spread of Covid-19. Results of the sero survey should be out in September.
In a sero survey, a group of individuals undergoes 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. This helps identify individuals who have recovered from infections. In July, the first sero survey was conducted with samples from 6,936 individuals, in three wards, in collaboration with NITI-Aayog and the Tata Institute of Fundamental Research (TIFR).
“We need comparative data to see the nature of the spread in two phases. This has to be done in the same places, though not on the same individuals,” said Suresh Kakani, assistant commissioner, BMC.
For the second survey, which is expected to start by the end of this week, BMC will test 6,200 individuals from slums and non-slum areas in Tilaknagar and Chembur in M (West) ward; Matunga, Sion and Wadala in F-North ward; and Dahisar and Mandapeshwar in R (North) ward. Officials started sensitisation and awareness programmes on antibody testing in these areas from August 10.
“It is essential to undertake the survey in the same areas to understand if the pandemic curve has actually flattened or more people are getting undiagnosed. For instance, in the first sero survey, BMC found 57% infection prevalence in slums. So, in the second survey, we have to see if the presence of antibodies has declined or increased in the same crowd. Also, there is a need to include more areas as each ward has its own demographic prevalence,” said Dr Lancelot Pinto, pulmonary medicine specialist at PD Hinduja Hospital.
Last week, principal investigator of the survey and a professor at TIFR, Ullas S Kolthur held an online interaction on the survey with fellow TIFR professor Sandeep Juneja. They said these three wards had been selected due to the high prevalence of Covid-19 cases at the beginning of June.
“F (North) and M (West) are neighbouring wards, which are also closer to G (North) ward which covers Dharavi, the biggest slum in Mumbai. As we didn’t want to cover such a big slum area, we decided to take the surrounding two wards to gauge the extent of the spread of infection. Also, we had to take one ward which is in the northern part of Mumbai so we decided to take R (North) where cases were showing a gradual rise [since June],” said Juneja.
Dr Behram Pardiwala, internal medicine expert, Wockhardt Hospital, said the scope of the sero survey should be extended to other civic wards. “Experts should focus on a more general population. This will help to provide a better picture of the exposure of the virus demographically,” he said.
BMC said it would decide on expanding the sero survey after the conclusion of this second round. “We are already in talks to include more areas but that would be done after the conclusion of the second survey,” said Kakani.
As HT had reported earlier, BMC faced a lot of resistance from individuals in non-slum residential areas during the first sero survey. Compared to the original target of 4,000 people from non-slum areas, field workers managed to collect samples from 2,702. This time around, BMC has been conducting door-to-door surveys in the three wards since August 10, to raise awareness about the survey.
“We have started with fieldwork where volunteers are conducting workshops and sensitizing people from residential areas about the sero survey and its importance,” said Kakani.
Sandhya Nandekar, ward officer of R (North) ward, said, “Slum dwellers are more co-operative than those from residential societies. Those in slums voluntarily come forward whereas the latter hid because from fear of getting quarantined.”
HT spoke to field workers involved in collecting blood samples in Matunga who said they were often insulted by residents and housing society members.
“There is so much fear among people of getting diagnosed with Covid-19 that they won’t even allow us to go inside. Guards were asked to keep the gates locked. Several housing society members would behave rudely and make us go away,” said one field worker.
