A staff member of epidemic prevention and control stands guard at a residential compound in Huanggu District in Shenyang, northeast China's Liaoning Province, Jan. 6, 2021. Shenyang is experiencing a strong cold wave that started on Wednesday, as the temperature dropped to near minus 20 degrees Celsius. (Xinhua/Yao Jianfeng)

A staff member of epidemic prevention and control is seen at a residential compound, identified as a medium-risk zone for COVID-19, in Huanggu District in Shenyang, northeast China's Liaoning Province, Jan. 6, 2021. Shenyang is experiencing a strong cold wave that started on Wednesday, as the temperature dropped to near minus 20 degrees Celsius. (Xinhua/Yao Jianfeng)

A police officer works at Huanggu District in Shenyang, northeast China's Liaoning Province, Jan. 6, 2021. Shenyang is experiencing a strong cold wave that started on Wednesday, as the temperature dropped to near minus 20 degrees Celsius. (Xinhua/Yao Jianfeng)

A staff member of epidemic prevention and control delivers supplies at a residential compound, identified as a medium-risk zone for COVID-19, in Huanggu District in Shenyang, northeast China's Liaoning Province, Jan. 6, 2021. Shenyang is experiencing a strong cold wave that started on Wednesday, as the temperature dropped to near minus 20 degrees Celsius. (Xinhua/Yao Jianfeng)

A staff member works at a nucleic acid testing site in Heping District, Shenyang, northeast China's Liaoning Province, Jan. 6, 2021. Shenyang is experiencing a strong cold wave that started on Wednesday, with the lowest temperature approaching minus 24 degrees Celsius. Shenyang has started conducting the second round of nucleic acid tests for residents in nine districts covering most urban areas to screen for coronavirus infections from Jan. 4. (Xinhua/Yang Qing)