Chinese authorities are enforcing restrictions on movement in major cities as the country grapples with the biggest spike in coronavirus disease 2019 (Covid-19) infections since the beginning of the pandemic.

China confirmed late Monday 125 new cases of the novel coronavirus nationwide amid the spread of the highly contagious Delta variant, including in the eastern city of Yangzhou in Jiangsu Province.

Authorities identified a Covid-19 cluster after an infected individual with the surname Wang came into close contact with 23 individuals, according to the Commission for Discipline Inspection of Yangzhou City on Monday.

Authorities “disciplined” local officials who are being charged with allowing the disease to spread and for not isolating Wang after he allegedly tested positive for the virus as early as July 29, the Commission said.

Local digital media outlet Pengpai reported that Wang played cards last month at a mahjong club about the time he may have been infectious.

Cities in China have ordered mass testing of residents in response to the unprecedented spread of the Delta variant.

In Nanjing, 15 local Chinese Communist Party officials were blamed for failing to prevent an outbreak that began at a city airport, according to the Party’s anti-graft watching, the Financial Times reported Monday.

Last month, the airport was linked to the latest wave of outbreaks. People who visited the Nanjing airport reportedly flew to other parts of the country.

China has made no changes to plans to host the 2022 Winter Olympics in Beijing and has pursued a policy of lockdowns, strict border control and mass testing.

The country’s policy remains susceptible to fast-spreading viruses, however.

“China will have to pivot from its containment strategy, sooner or later,” said Chen Zhengming, an epidemiology professor at the University of Oxford, according to Bloomberg.

“You can stay Covid Zero for a while, but you can’t stay Covid Zero forever because the virus swoops in before you know it,” he said.