Mumbai, June 9 The Indian Council of Medical Research conducted the first population-based serosurvey in India that reveals around 15-30 per cent of people living in the containment zones have been exposed to the coronavirus. They were infected with the virus and recovered unknowingly, the New Indian Express reported.

The study was carried out to examine the penetration of the virus in containment areas and hotspots. The preliminary findings of the ICMR were shared with the Prime Minister’s Office.

In a serosurvey, blood samples are collected to assess the presence of antibodies responding to a specific pathogen. In this case, it was meant to test for IgG antibodies against SARS-CoV-2 that normally appears 14 days after the infection, and continue to be present in the blood serum for months.

The ICMR collected around 24,000 random blood samples from 70 districts with the help of the National Centre for Disease Control, World Health Organisation's India office and the State governments.

These included ten hotspot cities Mumbai, Ahmadabad, Pune, Delhi, Kolkata, Indore, Thane, Jaipur, Chennai, and Surat that contribute nearly 70 per cent of India's total case load. The authorities randomly picked 10 containment areas in each of these cities to collect 500 samples each.

In addition, 400 samples each from other 60 districts across 21 States — categorized on the basis of low, medium and high caseload — were also collected.

“Barring two hotspot cities Surat and Kolkata and six other districts, we now have results from all other sites and it shows that infection size in many containment areas in the worst-hit districts is 100-fold to 200-fold higher than the cases reported at those sites,” an official privy to the survey report said as quoted in the New Indian Express . The data for eight districts are still being analyzed and will be incorporated in the findings.

Another official quoted in the report said that sites, where infection size is 100 to 200 times higher, are mainly in Mumbai, Pune, Delhi, Ahmedabad and Indore.

“What we have understood so far is that the infection is much more widespread than what is reflected by the reported cases in many cities and containment efforts may not have fully paid off,” he said. “In tier II and tier III cities, on the other hand, the spread of the virus is minimal.”

In the survey, ‘ COVID Kavach Elisa’ was used to carry out antibody tests. The product is developed by the National Institute of Virology under the ICMR. The agency claims that the product has high specificity and sensitivity. In other words, the kit detects the presence of even low levels of antibodies against novel coronavirus almost accurately, the NIE report further added.

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