India had about 64 lakh Covid-19 infections by early May: National sero-survey

More than 64 lakh Indians were exposed to Covid-19 as against the official count of around 62,000 on May 10 – a jump of 100 times – demonstrating a silent spread of the virus escaping the detection net in the early months of the epidemic.

This is the finding of the Indian Council of Medical Research's own serological survey, which was not published so far, even though the government shared a few points from the survey in a press conference in June.

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“A cumulative 6,468,388 adult infections were estimated in India by the early May,” said the survey whose results have appeared in the Indian Journal of Medical Research.

For comparison, there were more than 56,000 laboratory-confirmed cases on May 8, which rose to 62,000 on May 10.

While disclosing the survey findings at a press conference in June, neither ICMR director general Balram Bhargava nor the NITI Ayog member Vinod Paul revealed the 64 lakh figure.

For every laboratory-confirmed Covid-19 case, there were 82-130 undocumented cases of infection, as per the survey that screened 28,000 people from 70 districts in 21 states. For the country as a whole, the seropositivity was 0.73%, suggesting the vulnerability of a large chunk of the adult population.

"The findings indicated that the overall seroprevalence in India was low, with less than one per cent of the adult population exposed to SARS-CoV-2 by mid-May 2020. The low prevalence observed in most districts indicates that India is in the early phase of the epidemic and the majority of the Indian population is still susceptible to SARS-CoV-2 infection," the survey report said.

However, several serosurveys carried out by the states showed the virus spread much more within the community as antibodies against Covid-19 were found among 29% people in Delhi, 16% in Mumbai, 51% in Pune, 28% in Punjab and 21% in Chennai. In Mumbai slums, the seropositivity rate goes up to 57%.

The survey has also estimated that infection fatality rate — the proportion of deaths among the total number of infections — in India ranged from 0.0018% in districts with least prevalence to 0.11% in districts with the highest prevalence on May 24. The numbers changed to 0.0027% to 0.15% on June 1.

However, the ICMR scientists admitted that the death figures might be a case of underestimation because of an inaccurate and incomplete system of death reporting. Currently, India’s case fatality rate, the proportion of deaths among laboratory Covid-19 cases, is 1.7%.

Earlier this month ICMR carried out a second round of serosurvey in the same districts but expanding the base this time. Every member of a family was sampled unlike the first one in which only one person from each family was selected. The results are likely to be out next month.

Meanwhile, the number of positive cases and Covid-19 deaths are on a steady rise. On Friday, 96,551 new cases were reported taking the tally to 45.62 lakh. For the first time, more than 1,200 deaths were recorded as the toll stands at 76271.