Residents wearing masks wait at a bus stop in Beijing Saturday, Sept. 18, 2021. China's "zero tolerance" strategy of trying to isolate every case and stop transmission of the coronavirus has kept kept the country where the virus first was detected in late 2019 largely free of the disease. (AP Photo/Ng Han Guan)

A man masks himself after getting a nuclei test for COVID-19 in Beijing Saturday, Sept. 18, 2021. China's "zero tolerance" strategy of trying to isolate every case and stop transmission of the coronavirus has kept kept the country where the virus first was detected in late 2019 largely free of the disease. (AP Photo/Ng Han Guan)

Visitors wearing face masks pose for photos near a large portrait of Chinese leader Mao Zedong on Tiananmen Gate near Tiananmen Square in Beijing, Saturday, Sept. 18, 2021. China's "zero tolerance" strategy of trying to isolate every case and stop transmission of the coronavirus has kept kept the country where the virus first was detected in late 2019 largely free of the disease. (AP Photo/Mark Schiefelbein)

FILE - In this Sept. 18, 2021, file photo, workers move a giant flower blossom as part of preparations for China's National Day holiday on Tiananmen Square in Beijing. China's "zero tolerance" strategy of trying to isolate every case and stop transmission of the coronavirus has kept kept the country where the virus first was detected in late 2019 largely free of the disease. (AP Photo/Mark Schiefelbein, File)

People wearing face masks to protect against COVID-19 walk past a display showing a countdown clock to the Beijing 2022 Winter Olympics in Beijing, Wednesday, Aug. 18, 2021. China's "zero tolerance" strategy of trying to isolate every case and stop transmission of the coronavirus has kept kept the country where the virus first was detected in late 2019 largely free of the disease. (AP Photo/Mark Schiefelbein)

FILE - In this May 2, 2021, file photo, a woman adjusts her face mask as she walks by a statue featuring the Beijing Winter Olympics figure skating on display at the Shougang Park in Beijing. China's "zero tolerance" strategy of trying to isolate every case and stop transmission of the coronavirus has kept kept the country where the virus first was detected in late 2019 largely free of the disease. (AP Photo/Andy Wong, File)

A vendor serves a customer wearing a mask in Beijing Saturday, Sept. 18, 2021. China's "zero tolerance" strategy of trying to isolate every case and stop transmission of the coronavirus has kept kept the country where the virus first was detected in late 2019 largely free of the disease. (AP Photo/Ng Han Guan)

A man gets swapped during a nuclei test for COVID-19 in Beijing Saturday, Sept. 18, 2021. China's "zero tolerance" strategy of trying to isolate every case and stop transmission of the coronavirus has kept kept the country where the virus first was detected in late 2019 largely free of the disease. (AP Photo/Ng Han Guan)