The Chinese city of Qingdao is testing its entire population of nine million people for Covid-19 over a five-day period.
The mass testing comes after the discovery of a dozen cases linked to a hospital treating coronavirus patients from abroad.
In May, China tested the entire city of Wuhan – home to 11 million people and the epicenter of the global pandemic.
The country has largely contained the virus.
This is in stark contrast to other parts of the world where the number of cases and lockdown restrictions of varying severity are still high.
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In a statement posted on Chinese social media site Weibo, the Qingdao Municipal Health Commission said six new cases and six asymptomatic cases were discovered.
All of the cases were linked to the same hospital, the Global Times said.
Chinese authorities now have a strategy of mass testing even when a new cluster of coronavirus appears to be relatively minor, correspondents said.
The commission added that a city-wide testing program had been launched, with five districts to be tested within three days – and the entire city to be tested within five days.
Some 114,862 people – including medical staff and patients newly admitted to hospitals in the city – have already tested negative for the coronavirus, he said.
Videos circulating online showed local residents lining up late Sunday to get tested, the Global Times said, adding that some of the test points were open from 7 a.m. to 11 p.m.
The new cases come a week after the Golden Week holiday in China – which has seen millions of people travel across the country.
A Global Times report citing the Qingdao Municipal Culture and Tourism Bureau said the city received 4.47 million passenger trips during this period.
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The neighboring city of Jinan, which is also in the same province as Qingdao, has called on anyone who has visited the city since September 23 to get tested for the virus, according to a report from The Paper.
Earlier last month, Qingdao announced that two city port workers who handled imported seafood had tested positive for the virus. However, they weren’t known to have infected anyone else.
Daily coronavirus infections have declined dramatically in China, and for the most part the country appears to have recovered from the worst of viruses.
China currently has 85,578 cases of the virus and the death toll stands at 4,634.
Earlier this year, China completed a mass testing program in Wuhan, saying 11 million people had been tested in 10 days.
However, the BBC’s Reality Check later estimated the figure to be closer to 9 million over 10 days – still a significant number of people.
Hundreds of testing centers have been opened, with thousands of testing staff involved.