Tianjin is a port city of 14-million people located just 70 miles southeast of Beijing. So when COVID cases were detected in Tianjin there was an immediate decision to test everyone in the city to make sure the virus couldn’t spread to the capital.

Officials in the northern Chinese port city of Tianjin, near Beijing, said on Sunday that its entire population of 14 million would be tested for the coronavirus after it was found in 20 residents, at least two of whom were infected with the fast-moving Omicron variant.

Mass testing over the weekend revealed another 20 people with the coronavirus, according to a report late Sunday by the city’s official news service…

Li Hongzhong, the Communist Party secretary for Tianjin, vowed that the city would “fulfill to the utmost” its role as a “moat” protecting Beijing, official news outlets reported.

Tianjin is only about 30-minutes from Beijing by high-speed train so people frequently travel back and forth for work. To avoid possible spread of Omicron to Beijing, trains and car traffic from Tianjin have been cut off:

Authorities have also sought to restrict travel from Tianjin to Beijing, which will host the Winter Olympics from February 4. Barricades have been set up on highways to Beijing and the sale of train tickets from Tianjin to Beijing has been halted.

University students in Tianjin have been told to stay on campus, while schools in the Binhai New Area – where most of the cases have been found – have been suspended…

Ginny Yang, a master’s student at Tianjin University, said they could only leave campus with a valid reason. “I feel so homesick now,” Yang said. “I managed to get through the first semester of my master’s but I’ll be so sad if I can’t [return home to] see my family.”

But another student at the university, Zora Kong, said she had managed to leave Tianjin on Saturday, a day before the travel restrictions began, and she was not the only one. “Some of my classmates have already travelled back home because they were worried about the situation in Tianjin deteriorating,” Kong said.

There is evidence that students who tried to avoid being cut off from traveling home have already spread the Omicron variant. A student from Tianjin who traveled to another city two weeks ago also brought along the Omicron variant:

But there were worrying signs that the Omicron variant had already spread beyond Tianjin. The central Chinese city of Anyang, in Henan Province, reported two local Omicron infections on Monday, traced to a student who had traveled from Tianjin on Dec. 28, spurring concerns that the Omicron variant may have already been circulating in Tianjin for nearly two weeks.

It seems possible some students might already have headed home to other cities, even to Beijing. So it remains to be seen if the zero-COVID policy China has used so far will work with the Omicron variant. Given how quickly Omicron spreads, this could either be under control or completely out of hand by the time the Olympics start on February 4.