A clinic doctor who was infected in a dance club worked in the Argyle Centre in Mong Kok. Photo: Google Maps

Hong Kong saw an increase in local infections with unknown sources on Wednesday as the Covid-19 virus spread to different districts in the city.

The Center for Health Protection said 85 cases were recorded, one imported and 84 local, within the 24 hours on Tuesday. Of the local patients, 63 were related to the “dance club cluster,” which is the biggest infected group in Hong Kong with 250 patients identified so far.

Dora Lau, a 75-year-old obstetrician and gynecologist who worked in clinics in Mong Kok and Ma On Shan, was among the cluster patients.

She told health officials she visited a dance club on November 17 and 19 and continued to work until she tested positive on Wednesday. A close contact person who studies at the Victoria Shanghai Academy in Aberdeen is waiting for a test result. The school will be closed for sterilization.

A 44-year-old woman who arrived from mainland China through Shenzhen Bay Port on November 8, finished the 14-day home quarantine on Sunday but showed symptoms on the same day. She stayed with a 52-year-old woman in a flat on Apliu Street in Sham Shui Po. Both tested positive on Tuesday.

Health officials were asked whether the 44-year-old was infected in mainland or Hong Kong. Chuang Shuk-kwan, head of the communicable disease branch of the Center for Health Protection, said it was more likely that she was infected by her flatmate, who got the coronavirus in Hong Kong.

Since Monday, tens of thousands of Hong Kong people staying in the mainland and Macau have been allowed to return to Hong Kong without being quarantined if they have negative test certificates. They can leave for Hong Kong under a daily quota of 5,000 people, including 3,000 through the Shenzhen Bay Port and 2,000 through the Hong Kong-Zhuhai-Macau Bridge. It is unclear whether any of these people could have been infected.

Patients with no known source amounted to 16 on Tuesday, compared with 10 on Monday. Untraceable cases were in different districts, including North Point, Tai Po, Tuen Mun, Causeway Bay, Shatin and Discovery Bay.

The patients included a 15-year-old student in Kiangsu-Chekiang College in North Point, a 27-year-old male nurse at the Gleneagles Hospital Hong Kong, a 21-month-old baby and some housewives and retired people.

Apart from these, about 60 people tested positive preliminary on Wednesday. An employee of the Siu King Care and Attention Home in To Kwa Wan was among them.

Infectious disease specialist Joseph Tsang Kay-yan said local infections would probably continue to grow in the coming two weeks as the current fourth-wave would be more severe than the the third one in summer.

Tsang said despite the government announcing on Tuesday that nightclubs, party rooms and bars would have to shut, it did not close karaoke and mahjong parlors, giving an impression that the situation was not very serious. He said he was worried that people could turn to spending time in karaoke and mahjong parlors, thinking these were safe.

Read: HK shuts bars and clubhouses as cases surge