China is battling its largest COVID-19 outbreak, which is caused by the highly transmissible delta variant, with some areas restricting entry by people from a northeastern city where infections have grown faster in the past week than elsewhere in the country.

According to Reuters calculations based on official data, a total of 1,308 domestically transmitted infections with confirmed symptoms were reported in the mainland between Oct. 17 and Nov. 14, surpassing the 1,280 local cases from a summer delta outbreak.

This is China’s largest delta outbreak, affecting 21 provinces, regions, and municipalities. Although it is smaller than many other outbreaks in other countries, Chinese authorities are eager to stop the spread in accordance with the government’s zero-tolerance policy.

A dozen province-level regions were able to contain their outbreaks within weeks due to the rapid implementation of a complex set of controls, including rigorous contact tracing, multiple rounds of testing of people in high-risk areas, the closure of entertainment and cultural venues, and restrictions on tourism and public transportation.

However, the northeastern city of Dalian is fighting the virus, according to Wu Liangyou, an official with the National Health Commission, who spoke at a news conference on Saturday.

According to Reuters, since the first local symptomatic patients from the latest outbreak were reported on Nov. 4, the city of 7.5 million people has detected an average of about 24 new local cases per day, more than any other Chinese city.

People arriving from Dalian were quarantined at centralized facilities for 14 days before being allowed to move freely in a few cities near Dalian, including Dandong, Anshan, and Shenyang.

As of Nov. 14, mainland China had reported 98,315 confirmed coronavirus cases with symptoms, including both domestically and internationally transmitted infections. There have been 4,636 fatalities.