Survey also showed that by May-June, infection had already spread to rural India.(Representational)
India may have had 6.4 million coronavirus cases by May, the first national sero-survey conducted by top medical body ICMR indicates. The survey, published in the Indian Journal of Medical Research, suggests that 0.73 per cent adults in the country were exposed to Covid-19.
The survey, carried out from May 11 to June 4, tested blood samples from 28,000 people across 21 states.
Sero-positivity was the highest in the age group of 18 to 45 years (43.3 per cent), followed by those between 46 and 60 years (39.5 per cent); it was the lowest among those above 60 (17.2 per cent).
A total of 64,68,388 adult infections were estimated in India by the early May, the survey report said.
For every confirmed case of COVID-19 in May, there were 82-130 infections that went undetected. The survey report said that overall infections were low with less than one percent of the adult population being exposed to COVID-19 by then. But this also meant that a majority of the population was still susceptible to the highly contagious virus.
"The findings of our survey indicated that the overall sero-prevalence 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 early phase of the epidemic and the majority of the Indian population is still susceptible to SARS-CoV-2 infection," said the report.
The survey also showed that around May and June, the infections had already spread to rural India.
India has been battling the Coronavirus for a few months now but the possibility of a shift in cases from urban areas to the country's small towns and villages is worrying.
A bulk of the rural Coronavirus numbers are likely to come from states like Uttar Pradesh and Bihar where a sizeable population lives in villages and small towns.
Even in districts with zero or low number of detected cases of Covid, people were found to be infected. This could be due to low testing and poor access to testing labs which led to under-detection of cases in these districts. The survey suggested that there was a need to strengthen surveillance and increase testing of suspected cases in these areas. The report said, "The present findings of seropositivity in the strata of districts with zero to low incidence of COVID-19 cases underscores the need to strengthen surveillance and augment the testing of suspected cases in these areas."
Sero-positivity was highest at 69.4 per cent in the rural areas (villages) while in the urban slums it was 15.9 per cent and in urban non-slums it was recorded at 14.6 per cent.
But the survey was also done mostly in rural areas. The survey says that only about one-fourth (25.9 percent) of the surveyed clusters were from urban areas.
It highlighted the need to continue to implement specific containment measures including the testing of all with symptoms, isolating positive cases and tracing high-risk contacts to slow transmission and to prevent the overburdening of the health system.
Men living in urban slums and in occupations with high risk of exposure to potentially infected persons were associated with sero-positivity.