Chennai: Three out of 10 people had tested positive for antibodies to SARS-CoV-2 — the virus that causes Covid-19 — as of November 2020 in Tamil Nadu, shows a serological study done by the directorate of public health. The findings, which are yet to be peer reviewed, show that more than 2.3 crore people in the state were infected until last November — nearly 36 times the number of people who had officially tested positive for Covid-19 infection.
The representative study done in association with scientists from the US between October and November 2020 showed that the average sero-prevalence in TN was 31.5% — ranging from 11.1% in the Nilgiris to 51.05% in Perambalur district. Chennai, one of the worst affected districts in TN, had 40.9% sero-positivity. Coimbatore had 20.4%, Trichy 32% and Madurai had recorded 38% sero-positivity.
“This means several people who got the infection never knew they had been infected. The 0.052% infection fatality rate for the period was far lower than the present case fatality rate of 1.5% which uses total positive cases as a denominator,” said director of public health Dr T S Selvavinayagam.