Each cluster consisted of 30 participants drawn randomly from a village of a rural area or a street in urban area. Blood samples were collected and tested for the presence of SARS COV-2 IgG antibodies using Chemiluminescence based Immuno Assay (CLIA). Highest seropositivity of 84 per cent was observed in Virudhunagar, followed by Tenkasi, Chennai, Madurai and Theni. The lowest seropositivity of 51 per cent was reported in Karur. Four districts—Perambalur, Ariyalur, the Nilgiris and Karur—reported seropositivity of less than 60 per cent.
