China’s omicron outbreak spread to its major e-commerce hub days ahead of the Lunar New Year break, the latest of a slew of flareups putting holiday plans for millions of people at risk.

At least seven infections were detected in Hangzhou, a city near Shanghai and home to Alibaba Group Holding Ltd. and fintech giant Ant Group Co. There are concerns that cases may increase after one of the patients attended a company gathering along with several hundred people.

Several employees at Alibaba and Ant said they hadn’t yet been subjected to mandatory companywide testing, as their campuses are located away from the epicentre of the flareup. A representative for Ant declined to comment, while a spokesperson for Alibaba didn’t immediately respond.

In the north of the country, the major port city of Tianjin reported one new infection just a day after cases had dropped to zero. The re-emergence of omicron followed an almost three-week containment effort that disrupted production at Toyota Motor Corp. and Volkswagen AG. While nearby Beijing has managed to limit its recent omicron flareup to six people, it continues to grapple with a worsening delta cluster that’s centred on cold-storage facility workers.

The spread comes just days away from the weeklong New Year break that typically sees hundreds of millions of Chinese people traverse the country to visit their families and home towns. Concerns that those journeys may seed further outbreaks have prompted warnings from some local authorities in lower-tier cities against people returning from places that have recently reported infections.

The cases also underscore the challenges China faces in pushing forward with the Covid Zero ambitions that have made it a global outlier. The ongoing spread of the virus has come despite some of the strictest containment measures in the world, including border restrictions and lockdowns for even single-digit rises in infections, and is likely to test how practical it will be to entirely stamp out the more transmissible omicron variant.

China reported 23 Covid cases among people involved with the Olympics, which start on Feb. 4. Cases have been rising in Beijing despite the capital’s stringent measures but authorities are less likely to enact the harsh restrictions that have been imposed on smaller cities over similar flareups.

On Thursday, the country reported 42 domestic infections, including 17 that are symptom-free. The northeastern province Heilongjiang reported 16 infections, while western outpost Xinjiang continues to find infections near its border with Kazakhstan. The city of Anyang, which has been fighting against omicron spread from Tianjin, had one infection.

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