The study used a sample of 34,000 people in the general population in Wuhan — the original epicenter of the pandemic — and other cities in Hubei province, as well as Beijing, Shanghai, and the provinces of Guangdong, Jiangsu, Sichuan and Liaoning to estimate Covid-19 infection rates.

The researchers found an antibody prevalence rate of 4.43% for Covid-19 among residents in Wuhan, a metropolis of 11 million people. As of Sunday, Wuhan had reported a total of 50,354 confirmed cases of Covid-19, according to the Wuhan Municipal Health Commission.

The study aimed to estimate the scale of past infections in a population by testing blood serum samples from a pool of people for coronavirus antibodies. Its findings are not taken to be final statistics of how many people in a given area have been exposed to the virus.