More than half the residents of slums in three areas in Mumbai, tested positive for antibodies to the coronavirus, a new survey has found.
Only 16% of people living outside slums in the same areas were found to be exposed to the infection.
The results are from a random testing of some 7,000 people in three densely packed areas in early July.
Mumbai has reported more than 110,000 cases and 6,187 deaths as of 28 July.
The survey carried out by the city’s municipality, the government think-tank Niti Aayog and the Tata Institute of Fundamental Research.
It found that 57% of the people tested in slum areas of Chembur, Matunga and Dahisar had been exposed to the novel coronavirus.
Some 1.5 million people live in these three areas located in the western, eastern and central parts of the city.
The high prevalence rate could partly be explained by the fact that residents share common facilities such as toilets.
than 110,000 confirmed cases of Covid-19
“The results showed how crowding plays a key role in the spread of the infection,” Dr Sandeep Juneja of Tata Institute of Fundamental Research (TIFR) told Media.
The study also found that a large section of people had been infected and survived with no or little symptoms, leading to a low fatality rate in these areas – one in one thousand to one in two thousand. This also lowers the city-wide death rate from Covid-19.
And more women were found to have been exposed to infection by the virus in both slum and non-slum areas.
With the cases slowing down in Mumbai, the survey also raises the question whether the city is approaching herd immunity to the infection. Mumbai reported 717 new infections on Tuesday, the lowest in three months.
“The jury is still out on that. For one, we still don’t know how long the immunity to the infection lasts. We will only know the answer after repeat surveys,” Dr Kolthur says.
India’s worst-hit city
Earlier this month a government survey found that nearly one in four residents in India’s capital, Delhi, has been exposed to coronavirus infection.
The government survey said 23.48% of the 21,387 people whose blood samples were tested had Covid-19 antibodies.