People take part in a new round of COVID-19 nucleic acid test at a residential community which has been classified as a high-risk area in Daxing District, Beijing, capital of China, Feb. 4, 2021. (Photo: Xinhua)

People take part in a new round of COVID-19 nucleic acid test at a residential community which has been classified as a high-risk area in Daxing District, Beijing, capital of China, Feb. 4, 2021. (Photo: Xinhua)

People take part in a new round of COVID-19 nucleic acid test at a residential community which has been classified as a high-risk area in Daxing District, Beijing, capital of China, Feb. 4, 2021. (Photo: Xinhua)

Combo photo shows a health worker escorting a senior resident on the way home during a new round of COVID-19 nucleic acid test at a residential community which has been classified as a high-risk area in Daxing District, Beijing, capital of China, Feb. 4, 2021. (Photo: Xinhua)