Shanghai's recent COVID-19 resurgence related to multiple KTVs was caused by the same Omicron sub-variant as the city's novel coronavirus outbreak in early March.



The more contagious and faster-spreading BA.5 sub-variant has been detected in the recent outbreak in Xi'an in northwest China's Shaanxi Province and the capital Beijing.



However, according to gene sequencing, all the infections of the ongoing flare-up in Shanghai are the Omicron BA.2.2 subvariant, the city's COVID-19 prevention and control authority said on Thursday.



Between July 3 and 6, a total of 74 COVID-19 positive cases were linked to a KTV and a tea house at 148 Lanxi Road in Putuo District, the epicenter of the city's new round of the pandemic.



About 80 percent of the positive cases had been to KTVs. Their traces had covered seven KTVs in five local districts, the authority said.



"A cluster of people was exposed in the same enclosed environment at these KTVs, triggering rapid transmission of the virus in a short period of time," the epidemiological investigation report revealed.



They had later been to many public venues and caused the virus to spread wider across the city, it added.



The authority warned that the "concealing community transmission risk" still exits, because the cluster infection centered on the Putuo site had spawned a wide spread of positive cases who had active social movements.



Residents are being asked to enhance self-protection and receive regular nucleic acid test. They should also scan the venue code actively and get COVID-19 vaccines as soon as possible.



Shanghai designated 26 high- and medium-risk areas for COVID-19 on Wednesday after detecting a host of new infections linked to the Lanxi Road KTV and tea house.



Business licenses of the KTV and the tea house have been revoked, while two officials have been reprimanded and are under investigation.



Shanghai reported 32 locally transmitted confirmed cases and 22 local asymptomatic infections on Wednesday, the highest number since the city emerged from its over two-month lockdown in June.