A staff member of epidemic prevention and control stands guard at the entrance of a residential compound in Huanggu District, Shenyang of northeast China's Liaoning Province, Jan. 4, 2021. A total of 16 areas have been identified as medium-risk zones for COVID-19 in Shenyang, with prevention and control measures in place, local health authorities told a press briefing here on Monday. (Xinhua/Yao Jianfeng)

A police officer stands guard at the entrance of a controlled area in Huanggu District, Shenyang of northeast China's Liaoning Province, Jan. 4, 2021. A total of 16 areas have been identified as medium-risk zones for COVID-19 in Shenyang, with prevention and control measures in place, local health authorities told a press briefing here on Monday. (Xinhua/Yao Jianfeng)

A staff member of epidemic prevention and control measures body temperature for people aboard a vehicle about to enter a residential compound in Huanggu District, Shenyang of northeast China's Liaoning Province, Jan. 4, 2021. A total of 16 areas have been identified as medium-risk zones for COVID-19 in Shenyang, with prevention and control measures in place, local health authorities told a press briefing here on Monday. (Xinhua/Yao Jianfeng)

Staff members of epidemic prevention and control stand guard at the entrance of a controlled area in Huanggu District, Shenyang of northeast China's Liaoning Province, Jan. 4, 2021. A total of 16 areas have been identified as medium-risk zones for COVID-19 in Shenyang, with prevention and control measures in place, local health authorities told a press briefing here on Monday. (Xinhua/Yao Jianfeng)

A staff member of epidemic prevention and control delivers grocery for residents at the entrance of a residential compound in Huanggu District, Shenyang of northeast China's Liaoning Province, Jan. 4, 2021. A total of 16 areas have been identified as medium-risk zones for COVID-19 in Shenyang, with prevention and control measures in place, local health authorities told a press briefing here on Monday. (Xinhua/Yao Jianfeng)

Staff members of epidemic prevention and control deliver grocery for residents at the entrance of a controlled area in Huanggu District, Shenyang of northeast China's Liaoning Province, Jan. 4, 2021. A total of 16 areas have been identified as medium-risk zones for COVID-19 in Shenyang, with according prevention and control measures in place, local health authorities told a press briefing here on Monday. (Xinhua/Yao Jianfeng)

A police officer explains prevention and control rules to a resident at the entrance of a controlled area in Huanggu District, Shenyang of northeast China's Liaoning Province, Jan. 4, 2021. A total of 16 areas have been identified as medium-risk zones for COVID-19 in Shenyang, with according prevention and control measures in place, local health authorities told a press briefing here on Monday. (Xinhua/Yao Jianfeng)

A staff member of epidemic prevention and control passes on take-out for a resident at the entrance of a residential compound in Huanggu District, Shenyang of northeast China's Liaoning Province, Jan. 4, 2021. A total of 16 areas have been identified as medium-risk zones for COVID-19 in Shenyang, with according prevention and control measures in place, local health authorities told a press briefing here on Monday. (Xinhua/Yao Jianfeng)