A 25-year-old woman working in the Shanghai Songjiang District Central Hospital became a confirmed COVID-19 local case on Wednesday.

The woman, who lives in the district, had not been out of the city over the previous 14 days, and the disease prevention and control authority was racing against time to conduct genetic sequencing of the virus that she contracted, said Wu Jinglei, director of the Shanghai Municipal Health Commission.

"So far we don't find any relation of the case with the wave of local infection in other parts of the country," Wu said during a municipal media conference on Wednesday.

The nucleic acid test of the case, who had completed COVID-19 vaccination, showed an abnormal result earlier that day when the hospital screened all the staff regularly, according to the hospital.

"Her results in August had always been negative before today. Hospital staff in medical institutions in Shanghai are screened with the nucleic acid test once every three days," Wu said.

By 6 pm Tuesday, 10 close contacts of the case had been identified and put under hotel quarantine. Their nucleic acid tests are all negative.

A total of 66 secondary close contacts of the case in Shanghai had been identified and put under hotel quarantine, as well. All of their first-time nucleic acid tests were negative.

Also, 7,347 relevant individuals had been screened and their nucleic acid tests were all negative.

A residential community on Cangfeng Road in the district, where the case lived, was categorized as a medium-level region regarding the risk of the virus' spread. The hospital was put under closed-loop management.