Around the world, if someone tests positive for COVID-19, it is a confirmed case. But that is not always how it works in China.
Official documents show that China does not count asymptomatic carriers of the virus in its tally of confirmed cases. That practice is not consistent with the World Health Organization’s guidance, and it skews the Chinese data that epidemiologists have relied on to model how the virus spreads.
China publicly changed the criteria for tracking infections a few times early on in the outbreak. In January, when the infections started surging exponentially, China’s Health Commission decided that people without symptoms should not be included in the confirmed case count.