COVID-19 prevention and control workers check trucks passing a tollgate in Gaocheng district, Shijiazhuang, on Wednesday. (WANG ZHUANGFEI / CHINA DAILY)

Shijiazhuang in Hebei province has in recent days stepped up its fight against a COVID-19 outbreak. By Thursday, Hebei reported 523 confirmed locally transmitted cases and 320 asymptomatic cases since Jan 2. Medical workers from other parts of China have been sent to Hebei to offer front-line assistance, while thousands of prefabricated rooms were being constructed in the city's Gaocheng district, a high-risk area of infection. By Wednesday, more than 5,400 residents from the worst-hit villages in Gaocheng had been transferred to centralized quarantine facilities, local authorities said.

A medical worker collects a swab sample from a child in Shijiazhuang, Hebei province, on Monday. (WANG ZHUANGFEI / CHINA DAILY)

In the negative pressure isolation inflatable facilities of Huo-Yan Laboratory, tens of thousands of nucleic acid tests are carried out simultaneously by automated arms and other cutting-edge equipment. (WANG ZHUANGFEI / CHINA DAILY)

Traders at a vegetable wholesale market on Monday. (WANG ZHUANGFEI / CHINA DAILY)

Members of the nonprofit organization, Shijiazhuang Blue Sky Rescue, prepare to launch a drone to spray disinfectant at a residential community on Jan 7. (PHOTO PROVIDED TO CHINA DAILY)

A resident picks up a package from a courier at the entrance of a community on Jan 8. (TIAN MING / FOR CHINA DAILY)

Supermarket workers pack goods for online orders on Monday, for delivery to customers who are quarantined at home. (JIA MINJIE / FOR CHINA DAILY)

A disease prevention and control worker moves the luggage of a resident from Zengcun township in Shijiazhuang to a building at an isolation site on Wednesday. Authorities on Monday began to shift more than 20,000 villagers in Zengcun to centralized quarantine facilities by chartered buses, as part of an effort to rein in the COVID-19 outbreak. (WANG ZHUANGFEI / CHINA DAILY)

Volunteers ask a driver to scan a code to register at the entrance of a residential community on Saturday. (JIA MINJIE / FOR CHINA DAILY)