A serological survey conducted by the Brihanmumbai Municipal Corporation, Niti Aayog and Tata Institute of Fundamental Research showed that 16% of the people living in apartment buildings had been infected by the virus that causes Covid-19.
With 60% of Mumbai’s population living in slums, the study is likely to provide pointers on opening up the economy, herd immunity and fatality rates.
It showed that the infection fatality rate is quite low at 0.05% to 0.1%, meaning the virus is not as fatal in the city as it has been worldwide. This survey shows that Mumbai has one of the highest sero prevalence recorded by cities”.
The serological survey, which looks for antibodies in the blood, was carried out in the Chembur, North Wadala and North Dahisar areas in the first week of July and 6,936 samples were collected. Infection levels in women were higher than in men.
“These results will be valuable to learn more about herd 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,” according to the survey report.
Herd immunity is attained when a large proportion of a population develops resistance to the virus, curbing its ability to spread.
Civic and government officials have been taken aback by the survey’s findings, which put a question mark on the effectiveness of measures that the BMC had taken to contain the spread of the virus.
“The results are shocking because obviously our containment and chase-the-virus policy has worked to a very limited extent,” a civic official said. “The results will take the sheen from our work in slums like Dharavi, where there is all likelihood of a large section of people being infected and recovering from it, without the people or us knowing about it.”
The findings also suggest that Mumbai could possibly have the highest level of infections in the world because most serological surveys globally show a prevalence 14% to 25%.
A state government official said that if the second phase of the survey throws up similar results, it could spur the government to open up the economy sooner.
“Antibodies tell us that a person has already been infected and if we find more people have already been infected and have recovered, then… that would give a good idea on opening up the economy,” the official said.