New Delhi: At least 10 to 30 per cent of the population are already exposed to the COVID-19 virus — more than the number of cases being detected — a recent study of the Indian Council of Medical Research has revealed. All these are in COVID-19 hotspots or containment zones, which are getting sealed as soon as one case is being reported. Also Read - West Bengal Lockdown News: Kolkata, Howrah, North 24 Parganas District Likely to go Under Complete Lockdown For 14 Days

This was the first population-based serosurvey in India, conducted to assess the extent of exposure to SARS-CoV-2, conducted by the ICMR. The findings of the study have been shared with the Union cabinet secretary and the Prime Minister’s Office. Also Read - Coronavirus in Bihar Reaches CM Nitish Kumar's Doors as Niece Tests Positive

According to the study, in several containment areas, 15 to 30 per cent of the population has been exposed to the infection. Also Read - Music Therapy For Corona Patients in Lucknow Hospital

How was this survey conducted?

This is known as serosurvey in which blood samples of people are collected to test for the presence of antibodies specific to a pathogen. In this case, it was meant to test for IgG antibodies against SARS-CoV-2 that normally appear 14 days after the infection and continue to be present in the blood serum for months, reported the New Indian Express.

70 districts, 24,000 samples

The ICMR had collected nearly 24,000 samples from 70 districts in the country from randomly picked individuals residing in COVID-19 hotspots.

These included ten hotspot cities Mumbai, Ahmadabad, Pune, Delhi, Kolkata, Indore, Thane, Jaipur, Chennai and Surat that contribute nearly 70 % of India’s total caseload. 500 samples each were collected from 10 randomly chosen containment areas in each of these cities.

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 said the Express.

The cities which have shown the maximum number of such spread of infections are Mumbai, Pune, Delhi, Ahmedabad and Indore.