A policeman guides traffic at a road checkpoint in Beijing, capital of China, Aug. 6, 2021. Beijing has stepped up the screening of people entering the city from areas with reported COVID-19 cases. Airports and traffic nodes in the city are being asked to strengthen their prevention and control measures to halt the spread of the coronavirus. (Xinhua/Chen Zhonghao)

Policemen check information of people entering Beijing at a road checkpoint in Beijing, capital of China, Aug. 6, 2021. Beijing has stepped up the screening of people entering the city from areas with reported COVID-19 cases. Airports and traffic nodes in the city are being asked to strengthen their prevention and control measures to halt the spread of the coronavirus. (Xinhua/Chen Zhonghao)

A policeman checks information of people entering Beijing at a road checkpoint in Beijing, capital of China, Aug. 6, 2021. Beijing has stepped up the screening of people entering the city from areas with reported COVID-19 cases. Airports and traffic nodes in the city are being asked to strengthen their prevention and control measures to halt the spread of the coronavirus. (Xinhua/Chen Zhonghao)

A policeman asks people entering Beijing to scan a QR code to register travel information at a road checkpoint in Beijing, capital of China, Aug. 6, 2021. Beijing has stepped up the screening of people entering the city from areas with reported COVID-19 cases. Airports and traffic nodes in the city are being asked to strengthen their prevention and control measures to halt the spread of the coronavirus. (Xinhua/Chen Zhonghao)