India had estimated 74 million Covid cases by August

Nearly seven per cent of India's population aged ten and above was exposed to SARS-CoV-2, amounting to an estimated 74.3 million infections by August, with the seroprevalence being highest in urban slum areas followed by urban non-slum and rural areas, the findings of ICMR's second national serosurvey stated. According to the findings which have appeared in the Lancet Global Health pre-print, the overall seroprevalence of below 10 per cent in India indicates that a large proportion of the population remains susceptible to novel coronavirus infection.

"The transmission of infection is expected to continue in most Indian states till the herd immunity threshold is achieved, either by natural infection or vaccination. While this threshold is unknown, most estimates place it above 50 per cent," the report said. It stated that one in nine individuals who did not report any COVID-19-related symptoms in the past had the presence of SARS-CoV-2 IgG antibodies, indicating asymptomatic seroconversion among the general population in India. Seroconversion was also documented among individuals without a history of known contact with a COVID-19 case, and among those without any prior SARS-CoV-2 testing.

The adult seroprevalence increased ten times between May and August 2020. Lower infection to case ratio in August compared to May reflects a substantial increase in testing across the country," the findings stated.  The seroprevalence was higher in slum areas of Mumbai (57·8 per cent) compared to non-slum areas (17·4 per cent).Transmission will increase further in these rural areas in the coming months,