India's Covid-19 death toll estimated at 4.9 million, 10x the official figure: study

India's excess deaths during the Covid-19 pandemic could be as high as 4.9 million, a new study shows, providing further evidence that millions more may have died from coronavirus than the official tally.

The report by the Washington-based Center for Global Development, co-authored by India's former chief economic adviser Arvind Subramanian, included deaths from all causes since the start of the pandemic through June this year.

India's official tally of more than 414,000 deaths is the world's third highest after the United States and Brazil, but the study adds to growing calls from experts for a rigorous nationwide audit of fatalities.

A devastating rise in infections in April and May, driven largely by the more infectious and dangerous Delta variant, overwhelmed India's healthcare system and killed at least 170,000 people in May alone, official data show.

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Some experts have said excess deaths are the best way to measure the real toll from Covid-19. "For every country, it's important to capture excess mortality - the only way to prepare the health system for future shocks and to prevent further deaths," Soumya Swaminathan, the chief scientist of the World Health Organization, said on Twitter.