Youlu Apartments, a residential complex in suburban Shanghai's Songjiang District, will be unlocked and designated as a low-risk area at 12am on Wednesday, according to the city's health authorities.

The complex has been under closed-loop management and listed as a medium-risk area since a resident was diagnosed with COVID-19 on August 18.

The patient is a 25-year-old female medical worker at Songjiang District Central Hospital.

The woman was infected because she was exposed to a person or an environment bearing the overseas coronavirus due to her cursory prevention activity, the city's disease control and prevention center said.

Also, one of her close contacts, a 30-year-old man, was also diagnosed with COVID-19 while he was in quarantine at a designated place on August 25.

Apart from the man, all the other close contacts of the woman have tested negative since her infection.

As of Wednesday, there will be no medium-risk area in the suburban district.

In terms of the whole city, there will be four medium-risk areas from Wednesday – the residential complexes Jielonghuayuan and Qianhuiyuanyicun and the north area of Zhuheyuan, as well as Jinjiang Inn's Donghai Town branch, all of which are in the Pudong New Area, according to authorities.

They have been listed as medium-risk areas after five staffers from the foreign cargo aircraft area at the Shanghai Pudong International Airport were found infected with COVID-19 on August 20 and 21.

Last week, two more staff workers of the foreign cargo aircraft area tested positive. They all developed symptoms when they were under close-loop management at designated places, authorities revealed.

No locally transmitted cases have been reported so far in the city since last Friday.