A medical worker collects swab sample from a resident for nucleic acid testing in Harbin, northeast China's Heilongjiang Province, Sept. 22, 2021. Harbin, with a population of more than 10 million, launched citywide nucleic acid testing on Tuesday afternoon and plans to complete the campaign by the end of Thursday, according to the city's COVID-19 prevention and control headquarters. (Xinhua/Wang Song)
