Amy Kazmin in New Delhi
A new seroprevalence study in India’s southern state of Tamil Nadu has estimated that 31.6 percent of its 72 million residents have been exposed to the virus that causes Covid-19.
The results showed how the pathogen has spread far more widely than New Delhi officially acknowledges.
India has reported 10.8 million cases of coronavirus among its 1.4 billion residents – the second-highest number in the world, after the US – and about 154,000 deaths.
Tamil Nadu, the second most populous state in the country, has reported more than 800,000 infections and 12,000 deaths.
But public health experts said the reported number of cases in India underestimated how widely the virus has spread among the population. A nationwide seroprevalence study published last week by the Indian Council for Medical Research estimated that one in five Indians had been exposed to the virus in early January.
The study in Tamil Nadu, conducted between mid-October and the end of November by the state government and the IDFC Institute, tested 26,640 adults from a representative sample of the population for the presence of antibodies indicating previous infections caused by the Sars-CoV-2 virus .
The study found wide regional differences in seroprevalence across the state, with rates as high as 51 percent in some districts and only 11 percent in the sparsely populated region of The Nilgiris.
Overall, seroprevalence was higher in urban areas at 37 percent than in rural areas at 27 percent.
The study also found that seroprevalence was significantly higher in people of working age than the elderly, with people over 75 having an infection rate as low as 25 percent.
The study implied that at least 22.6 million people in Tamil Nadu were infected with Sars-CoV-2 in November, about 36 times the number of reported cases.