The Indian Council of Medical Research on Tuesday said it will begin antibody testing at the household-level to estimate the prevalence of Covid-19 infections among Indians. The survey will include 24,000 adults, distributed equally over four strata of districts that will be categorised on the basis of the spread of the infection.

The exercise will be done in collaboration with the Department of Health and Family Welfare, the Centre and the National Centre for Disease Control, the medical body said in an official statement. It will also get support from state health departments and key stakeholders, including the World Health Organization.

“This is a household-based survey of adults to look for presence of infection across the country in a systematic manner irrespective of reporting of cases currently,” ICMR researcher Dr Tarun Bhatnagar told The Indian Express. “It will look for presence of IgG antibodies that usually appear ten to fourteen days after infection,”

The survey would be conducted in 69 districts of 21 states and Union Territories, the medical body said. In each district, 400 random households in ten clusters will have one adult individual tested for Covid-19 antibodies in what is called a “sero survey”.

This test result will reveal if they have developed antibodies against the infection even though they are asymptomatic or show mild symptoms. Immunoglobulin G, or IgG, is a common type of antibody, which protects the body against infection.

“Sera from these individuals will be tested for presence of IgG antibodies using ELISA test [the enzyme-linked immunosorbent assay] developed by ICMR [and the] National Institute of Virology , Pune,” the medical body said. “The results of the survey will provide information about spread of SARS-CoV-2 infection [Covid-19] in different parts of the country.”

The exercise will help ascertain if there has been community transmission of the respiratory disease in these areas, an unidentified official told PTI. Officials added that the Indian Council of Medical Research had intended to start the study earlier with the rapid antibody testing kits for Covid-19 procured from China, but had to postpone it after these kits showed inaccurate results in some cases.

The Union health ministry will also begin hospital-based surveillance to monitor the trend of infection in all districts, PTI reported. The survey will be conducted at 10 health facilities – six public and four private hospitals – and would test outpatient attendees and pregnant women among the low-risk group, and healthcare workers among the high-risk population.

The number of coronavirus cases in India rose to 74,281 on Wednesday morning. The country reported 3,525 cases in the last 24 hours. The toll reached 2,415.

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