Local residents walk along the Nanjing Road in Shanghai (Photo: Global Times)

Shanghai reported one new local COVID-19 case and three imported cases on Saturday, the Shanghai Health Commission announced on Sunday, noting that the local patient lives in the Pudong New Area and is a co-worker of the airport freight security checker confirmed to have contracted the COVID-19 virus on Friday, with four close contacts under medical observation.

The three imported cases were Chinese citizens from the UK and the US, according to the Shanghai authorities.

The Mingtian Huacheng residential area in Zhoupu township in the Pudong New Area has been designated as a middle-risk region after a couple were found to be COVID-19 virus positive on Friday night.

The city followed strict rules to check all the patients' close contacts and disinfected all the areas they had been to under the closed-loop system. A total of 15,416 people were given nucleic acid tests. A 29-year-old man, who is a co-worker of the airport freight security checker confirmed to have COVID-19 virus on Friday, tested positive, Shanghai authorities announced on Saturday midnight.

The compound in Zhuqiao town in Pudong where he lives was labeled as a coronavirus mid-level risk area. Residents from mid-level risk areas are not allowed to leave Shanghai, and those who have to leave need to have negative nucleic acid tests certification.

The emergence of local cases shows there is a risk of COVID-19 outbreaks during the coming winter and spring, especially in the logistics and cold chain sectors, and the entire country faces this risk, Zhang Wenhong, a prominent Chinese infectious disease expert, noted at a press conference on Saturday.

The Shanghai Health Commission reminds residents to adopt necessary preventive measures including wearing masks, washing hands frequently, keeping social distance and avoiding directly touching cold-chain foods.