Less than one per cent of the population surveyed by the Indian Council of Medical Research (ICMR) in 83 districts, is believed to be exposed to SARS-CoV-2 virus, which causes Covid-19. As very few persons have been exposed to the virus, the Centre warned on Thursday that a large proportion of the population is still vulnerable to get infected. As a result, the Centre has also stated that local lockdown measures need to continue.
About 26,400 individuals from 83 districts, which were further divided into 770 clusters, were tested for IgG antibodies using Covid Kavach Elisa test, indigenously designed by the ICMR. “If a person is IgG positive, it means that he/she was infected with SARS-CoV-2 in the past,” said Balram Bhargava, Director General, ICMR. This is different from the routine reverse transcriptase polymerase chain reaction (RT-PCR) test carried out on throat or nasal swabs of individuals to confirm the presence of infection.
‘Lockdown must continue’
“Up to 0.73 per cent of the population in these districts had evidence of past exposure to SARS-CoV-2 virus. This means that a large proportion of the population is still susceptible, with risk in urban areas up to 1.09 times higher and that in urban slums up to 1.89 times higher. This means that infection can still spread, and that local lockdown measures need to continue as advised by the Centre,” said Bhargava. He added that the infection fatality rate, which means the per cent of deaths among those surveyed, was very low, only up to 0.08 per cent.
While the ICMR released results of the first part of the sero survey, which estimates the fraction of population infected by the virus in the general population, it is yet to release results of the estimated fraction of population which has been infected by the virus in containment zones of hotspot cities like Mumbai, Ahmedabad, Delhi, Pune and Indore.
Bhargava said the infection in containment zones was found to be high with significant variations. However, the study is still on and the data will eventually be shared with the states that will decide whether to increase or decrease the perimeter of containment.
In the sero survey, random blood samples were collected from individuals in districts that had previously reported either zero, few,, medium or high incidence of cases. A minimum of 15 districts from each of the four groups, and 400 individuals from each district were selected. Ten villages or urban wards were randomly chosen from these districts, and 40 adults were enrolled from each village or a ward, with one adult from each household.