The case, found in the financial district of Pudong on July 8, was linked with a case from overseas, said Zhao Dandan, vice-director of the city’s health commission.

Shanghai, in eastern China, emerged from a lockdown lasting around two months at the start of June, but it has continued to impose tough restrictions, locking down buildings and compounds as soon as new potential transmission chains emerge.

“Our city has recently continued to report more locally transmitted positive cases (of COVID-19) and the risk of the epidemic spreading through society remains very high,” Zhao of the Shanghai health commission warned.

He said residents in several major Shanghai districts would undergo two rounds of COVID tests, from July 12-14, in a bid to bring potential new outbreaks under control.

The Omicron BA.5 variant, which is driving a new wave of COVID-19 infections overseas, was first discovered in China on May 13 in a 37-year old male patient who had flown to Shanghai from Uganda, according to the China Center for Disease Prevention and Control.

Variant BA.5 has been shown to have an accelerated rate of transmission and an improved immune escape capability, said Yuan Zhengan, a member of the city’s expert advisory group on COVID prevention, speaking at the Sunday briefing.

But vaccination is still effective at preventing BA.5 from causing serious illness or death, he added.