• Around 7% of India’s adult population may have been exposed to the novel coronavirus till the last fortnight of August, according to the second national sero-survey by the Indian Council of Medical Research (ICMR).
  • This is roughly a 10-fold jump in numbers from the first sero-survey conducted by the Council across 70 districts in 21 States that sought to estimate the likely number of infected until early May. The people tested in the second survey were drawn from the same villages and clusters as the first, in which the scientists said that 0.73% of adults — or about 6.4 million — across the country were likely infected.
  • No figures were shared on the likely number of infections by ICMR but 7% of the population works out to about 62 million people. 

Sero-surveys are conducted by drawing blood samples and checking for a specific class of antibodies called IgG that appear within two weeks of an infection. Because it is yet unclear how long antibodies detectably persist in the body, their presence only indicates past exposure to — and not presence of — the virus.

  • During the first survey, it emerged that there were 82-130 infections for every confirmed COVID-19 positive case. That number has now dropped to 26-32 infections, which according to Dr. Bhargava, was the result of ramped up testing and early case detection.
  • In September, there were 29 million tests, compared to 23 million in August, 10.5 million in July and 30,000 in March.
  • However, the numbers also suggest that the country still has an overwhelming majority of its population yet to be exposed to the virus and therefore, is far from any peak or herd immunity levels. These refer to approximate estimates that show what percentage of the population needs to be exposed to the virus so that its spread is curtailed.

More risk in urban slums

  • “The risk of being exposed to the virus is real and we have to continue with our measures. Risk in urban slums is twice that of non-slums and four times that in rural settings,” Dr. Bhargava said.
  • One in fifteen individuals above 10 were exposed to the virus by August and there was no difference by age group and gender. 
  • “In light of upcoming festivities, winter season and mass gatherings, inventive