Shanghai scrapped about one-third of the flights from its busiest international airport on Friday and suspended some hospital services after a handful of Covid infections were detected in the financial hub, showing China’s commitment to stringent curbs to eliminate the virus as winter looms.

More than 30% of flights from Shanghai Pudong International Airport were canceled on Friday morning, state broadcaster CCTV reported. Schools were immediately suspended and housing complexes tied to the cases were locked down as local officials embraced strict measures in what may become a protracted battle as cold weather forces more people indoors.

Chinese airline stocks declined. Shanghai International Airport Co. Ltd. fell as much as 4%, while Cathay Pacific Airways Ltd. and China Eastern Airlines Corp. Ltd. dropped at least 2% in Hong Kong.

China reported four locally transmitted infections on Friday in Shanghai and the northern province of Liaoning, according to the country’s National Health Commission. Three other cases, all believed to be connected to the Shanghai flareup, were found in the e-commerce hub of Hangzhou - the capital of the Zhejiang province south of Shanghai - and Xuzhou in the north. None developed symptoms.

The news comes on the heels of the broadest outbreak China experienced since the virus emerged in 2019 in Wuhan, which had been brought to a trickle in recent days. The latest flareup comes amid strict measures to contain the pathogen and raises questions what it may take for China to get back to zero cases, which it has 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 and suspended emergency room services at some of its largest hospitals. Local authorities have already tested more than 54,000 people. No positive results have been reported so far. The renowned Zhejiang University closed one of its main campuses after a staff member tested positive.

Xuzhou, the 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. It also closed its subway system.