US coronavirus cases may be more than double official tally

By early March 2021, roughly 65 million people in the United States – or one out of every five people – had been infected by the coronavirus that causes Covid-19, a new analysis shows.

The findings, described in the Proceedings of the National Academy of Sciences, suggest that roughly 60 per cent of coronavirus infections had gone uncounted at that point – adding to a growing body of evidence that the pandemic’s true toll is far greater than official tallies show.

“It’s good to see people start estimating how far we potentially could be off,” said Jennifer Nuzzo, an epidemiologist at the Johns Hopkins Centre for Health Security, who was not involved in the study.

Scientists have long been aware that the official coronavirus numbers don’t capture the full story. One study that looked at life insurance applicants suggested the number of cases might have been twice as high as the official tally; another model suggested that deaths worldwide were roughly double the reported count.

But each of these estimates was limited by the data available to them. That’s a common theme for pandemic modellers: among three of the most well-known coronavirus data sources, each comes with a distinct disadvantage.

Going by the number of confirmed cases underestimates the actual number of infections, because not everyone who was infected was tested or diagnosed. The test positivity rate, meanwhile, tends to overestimate the true prevalence.