(Bloomberg) -- Covid-19 clusters have emerged in Shanghai and a neighboring city just as virus hotspots elsewhere in China recede, a sign the country’s fixation on continuing to eliminate all cases may become a protracted battle into the winter months.

China detected four locally transmitted infections Friday in the financial hub of Shanghai and the northern province of Liaoning, according to the country’s National Health Commission. Three other cases, reportedly connected to the Shanghai infections, were found in Zhejiang’s provincial capital of Hangzhou and in a small city in Zhejiang, though none the infected developed symptoms. 

The new flareup comes on the heels of the broadest outbreak China experienced since the virus emerged in 2019 in Wuhan and raises concern that the country may not be able to return to the Covid Zero status it has so aggressively sought. Officials have vowed to continue to battle the virus at every turn, prioritizing the health of its people, even as the rest of the world has gradually opened up.

Shanghai locked down residential compounds tied to the infections for 14 days, municipal government leaders said at a press conference late Thursday. Local authorities have already tested more than 54,000 people. No positive results have been reported so far. 

The flareup triggered an immediate suspension of schools, and the renowned Zhejiang University closed one of its main campuses after a staff member tested positive. Xuzhou, a city in Jiangsu that has one asymptomatic infection, shut down all schools and training institutes for three days effective on Friday to cut off transmission, local authorities announced at midnight. Shanghai has also suspended ER services at some of its large hospitals.

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