More than 232 000 people may have been infected in the first wave of Covid-19 in mainland China, four times the official figures, according to a study by Hong Kong researchers.

Mainland China reported more than 55 000 cases as of 20 February but, according to research by academics at Hong Kong University’s school of public health published in the Lancet, the true number would have been far greater if the definition of a Covid-19 case that was later used had been applied from the outset.

The Hong Kong study analyzed data up to 20 February culled from the World Health Organization’s mission to Wuhan.

It estimated that each of the first four changes increased the proportion of cases detected and counted, by between 2.8 and 7.1 times.

“If the fifth version of the case definition had been applied throughout the outbreak with sufficient testing capacity, we estimated that by 20 February 2020, there would have been 232 000 … confirmed cases in China as opposed to the 55 508 confirmed cases reported”, - reads the study.