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The national level sero-survey by the Indian Council for Medical Research (ICMR) has found that around 7 percent of India’s adult population may have been exposed to the novel coronavirus till the last fortnight of August.
- 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.
- The average prevalence in major cities ranged from 50% in Mumbai to 29% in New Delhi, 22% in Chennai and 7.8% in Indore.
What is a serological survey?
- A serological survey is done to detect the presence of specific antibodies, and is used to assess the prevalence of a disease in the population.
- The test indicates past infections (and which triggered an immune response), and is not used to detect active infections.
- A serological test is performed to diagnose infections and autoimmune illnesses. It can also be conducted to check if a person has developed immunity to certain diseases.
- 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.