High population, fewer Covid cases: BMC study on Mumbai wards inconclusive

Ahead of a third wave, BMC wants to study the pattern in wards with fewer Covid cases despite high population

The Brihanmumbai Municipal Corporation’s (BMC) month-long study, which started in the end of July, is inconclusive on why some civic wards reported fewer novel coronavirus cases despite high population. The BMC is now awaiting the results of the fifth serological survey in order to connect the dots with their initial findings of the study. Officials said this exercise will help them understand if sero prevalence was a factor leading to high or low burden of Covid-19 cases in some wards.

With study on Mumbai wards inconclusive, BMC is now awaiting results of sero survey to understand Covid pattern. (HT PHOTO)

HT had reported earlier that since the start of the pandemic in March 2020, wards A (Fort), B (Dongri) and C (Kalbadevi) saw the fewest infections among all 24 wards. For instance, on April 7 last year, when the city was at the peak of the first wave, these three wards had fewer than seven cases each. On the same day, however, G-South (Elphinstone) ward, by D (Nana Chowk), E (Byculla) and K-West (Andheri West) ward saw 78, 59, 46 and 43 cases, respectively, the highest number of patients across all wards.

The ward-wise difference is also visible in the data shared by the BMC. For instance, till September 6 this year, B ward recorded a total of 3,963 cases, the lowest in the city. It is followed by C and A wards, with 6,896 and 16,571 cases, respectively. On the other hand, K-W (Andheri West) has recorded 55,613 cases, the highest in the city. Similarly, R-Central (Borivli) and K-East (Andheri East) have registered 51,898 and 46,625 cases so far.

Anticipating a third wave, the BMC decided to study the infection pattern of Sars-CoV-2—the virus that causes Covid-19, but the results have been inconclusive. “We have found that some wards have performed more tests, which pushed their cumulative Covid-19 cases. But testing is directly proportional to the number of infected patients. A ward with more active patients will record more tests, as it also includes contact tracing. Thus, it doesn’t prove that testing is the only reason for ward-wise Covid-19 disparity,” said Suresh Kakani, additional municipal commissioner, BMC.

He also added that higher population was also considered as one of the contributing factors. A few crowded wards like L (Kurla) and M/East (Deonar, Govandi), with a population of more than 800,000 and 900,000, respectively (as per the Census 2011), recorded fewer Covid-19 cases. “We couldn’t find an explanation why some crowded wards recorded higher cases while others didn’t. The findings therefore haven’t been conclusive,” he added.

To understand if sero-prevalence was the reason behind fewer Covid-19 cases in some wards, the BMC has conducted a fifth ward-wise serological survey which will help them gauge how many people in a population have been infected with Covid-19 and have developed antibodies. The results are expected to be announced this week.

Dr Ramesh Bharmal, dean of BYL Nair hospital, Mumbai Central, stated that prevalence of a virus depends on various factors such as size of the population, movement of the public, demography and prevalence of antibodies. “As seen in the previous sero surveys, a large number of slum dwellers and younger population have developed antibodies which help curb fast transmission of the virus. So, there is a possibility that wards with higher young demography may have developed better resistance against the virus which is attributed in controlling its spread. This hypothesis can be established with the latest sero survey,” he said.

The BMC has predicted that the city could record 1.25 lakh Covid-19 cases in the anticipated third wave. So, it is essential for the BMC to chalk out the reasons behind ward-wise variation of Covid-19 cases, which will help them plan better if the city witnesses another surge, said BMC official.