Citizens register for COVID-19 tests at a testing station in Shibei District of Qingdao, east China's Shandong Province, Oct. 14, 2020. Over 5.6 million samples for nucleic acid testing have been collected by 8:30 p.m. on Tuesday in east China's Qingdao, after it began a city-wide testing campaign on Monday.

Citizens receive COVID-19 tests at a testing station in Shibei District of Qingdao, east China's Shandong Province, Oct. 14, 2020. Over 5.6 million samples for nucleic acid testing have been collected by 8:30 p.m. on Tuesday in east China's Qingdao, after it began a city-wide testing campaign on Monday. (Photos: Xinhua)

Health workers work at a testing station in Shibei District of Qingdao, east China's Shandong Province, Oct. 14, 2020. Over 5.6 million samples for nucleic acid testing have been collected by 8:30 p.m. on Tuesday in east China's Qingdao, after it began a city-wide testing campaign on Monday.

A health worker takes a swab sample from a citizen for COVID-19 test in Shibei District of Qingdao, east China's Shandong Province, Oct. 14, 2020. Over 5.6 million people had been sampled for nucleic acid testing by 8:30 p.m. on Tuesday in east China's Qingdao, after it began a city-wide testing campaign on Monday.