Qingdao residents joined long queues for testing centers after 12 infections were confirmed, mostly related to a city hospital, the national newspaper Global Times reported.
Qingdao Chest Hospital, which treats coronavirus patients who returned from overseas were locked up with buildings where infected people live.
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The Qingdao Municipal Health Commission said that testing five districts would take three days, with the entire city being completed two days later.
Test points would remain open until 11 p.m. to ensure medical teams can complete their work.
Qingdao’s new infections occurred soon after China had completed his Golden Week vacation, during which millions of people travel across the country to meet families.
Mass tests are carried out quickly in China to deal with epidemics of all sizes
In May, authorities tested almost all 11 million people in Wuhan – the city where COVID-19[feminine[feminine first appeared at the end of last year.
There have also been mass testing programs in Beijing and Urumqi.
Daily infections in the country have fallen sharply from peaks at the start of the year.
However, China remains on high alert to avoid further lockdowns, which previously led to a significant decline in the world’s second-largest economy.
According to the latest figures compiled by Johns Hopkins University, the number of confirmed cases of COVID-19 in China stands at 90,812. The death toll is 4,739.
The country continued to handle a number of cases involving travelers from overseas, but the last time there were reports of virus transmission in China was in August in Urumqi.
Travelers arriving from overseas to China are still required to undergo a 14-day quarantine.