Photo taken on Aug. 5, 2021 shows a mobile lab for COVID-19 nucleic acid testing in Wuchang District of Wuhan, Central China's Hubei Province. (Photos: Xinhua)

A medical worker works in a mobile lab for COVID-19 nucleic acid testing in Wuchang District of Wuhan, Central China's Hubei Province, Aug. 5, 2021.

A medical worker works in a mobile lab for COVID-19 nucleic acid testing in Wuchang District of Wuhan, Central China's Hubei Province, Aug. 5, 2021.

A medical worker works in a mobile lab for COVID-19 nucleic acid testing in Wuchang District of Wuhan, Central China's Hubei Province, Aug. 5, 2021.