A medical worker takes a swab sample from a resident for a nucleic acid test in Jinshui District of Zhengzhou, central China's Henan Province, May 7, 2022. Zhengzhou has carried out multiple rounds of nucleic acid testing to curb the COVID-19 resurgence. (Xinhua/Hao Yuan)

A medical worker takes a swab sample from a resident for a nucleic acid test in Jinshui District of Zhengzhou, central China's Henan Province, May 7, 2022. Zhengzhou has carried out multiple rounds of nucleic acid testing to curb the COVID-19 resurgence. (Xinhua/Hao Yuan)

An elder resident registers for a nucleic acid test in Jinshui District of Zhengzhou, central China's Henan Province, May 7, 2022. Zhengzhou has carried out multiple rounds of nucleic acid testing to curb the COVID-19 resurgence. (Xinhua/Hao Yuan)

A medical worker takes a swab sample from a resident for a nucleic acid test in Jinshui District of Zhengzhou, central China's Henan Province, May 7, 2022. Zhengzhou has carried out multiple rounds of nucleic acid testing to curb the COVID-19 resurgence. (Xinhua/Hao Yuan)

A medical worker takes a swab sample from a resident for a nucleic acid test in Jinshui District of Zhengzhou, central China's Henan Province, May 7, 2022. Zhengzhou has carried out multiple rounds of nucleic acid testing to curb the COVID-19 resurgence. (Xinhua/Hao Yuan)