One in four residents in the Indian capital, Delhi, have been exposed to coronavirus infection, a random sample antibody test suggests.
The survey said 23.48% of the 21,387 people whose blood samples were tested had Covid-19 antibodies.
It suggests that infections in the city are much more widespread than the number of confirmed cases indicates.
Delhi has so far recorded 123,747 cases, equivalent to less than 1% of its population of 19.8 million.
At 23.44%, the number of infections would be 4.65 million in a city that size. A government press release says the difference shows that “a large number of infected persons remain asymptomatic”.
It even says the figure of 23.48% may be too low because Delhi has several pockets of dense population. But it adds that “a significant proportion of the population is still vulnerable” and all safety measures must be strictly followed.
Experts say the random tests shows deep the infection has spread within the community and help authorities with better distribution of testing facilities.
Delhi has been one of the worst-hit cities in India and saw a chronic shortage of hospital beds in the first two weeks of June.
Over the past few weeks the number of daily cases and deaths have fallen.
India overall has recorded 11,92,915 infections with 28,732 deaths since the beginning of the pandemic.