An aerial view shows people lining up at a nucleic acid testing site during the second round of mass testing for the coronavirus disease (COVID-19), after local cases of the Omicron variant were detected in Tianjin, China January 12, 2022. The Chinese port city of Tianjin reported an increase in COVID-19 infections on Thursday as it stepped up efforts to rein in an outbreak that has spread the highly transmissible Omicron variant to another Chinese city. China Daily via REUTERS

People line up at a nucleic acid testing site during the second round of mass testing for the coronavirus disease (COVID-19), after local cases of the Omicron variant were detected in Tianjin, China January 12, 2022. Tianjin, located in northern China around 100 km (62 miles) from the capital Beijing, reported 41 domestically transmitted infections with confirmed symptoms on Wednesday, up from 33 a day earlier, data from the National Health Commission showed on Thursday. China Daily via REUTERS

A medical worker in protective suit collects a swab from a resident for nucleic acid testing at a makeshift testing site for the coronavirus disease (COVID-19), after local cases of the Omicron variant were detected in Tianjin, China January 11, 2022. Omicron has brought fresh challenges to China's strategy to quickly extinguish local outbreaks. cnsphoto via REUTERS

People line up for nucleic acid testing during a citywide mass testing for the coronavirus disease (COVID-19) after local cases of the Omicron variant were detected in Tianjin, China January 9, 2022. cnsphoto via REUTERS

People line up for nucleic acid testing during a citywide mass testing for the coronavirus disease (COVID-19) after local cases of the Omicron variant were detected in Tianjin, China January 9, 2022. cnsphoto via REUTERS

Community workers sort vegetables to be distributed to residents of an area under lockdown following the coronavirus disease (COVID-19) outbreak in Tianjin, where the Omicron variant has been detected, China January 12, 2022. cnsphoto via REUTERS