Health officials in Shanghai warned those returning from abroad to strictly comply with the post-quarantine rules Thursday after the city reported five coronavirus cases linked to an individual with international travel history.

The two symptomatic individuals who tested positive for the virus worked at a milk tea store in downtown Jing’an District, according to the Shanghai Municipal Health Commission. Both were close contacts of an individual who flew to Shanghai from the United States on Dec. 21.

The individual had undergone a 14-day quarantine at a centralized location and tested positive Tuesday, the last day of the weeklong self-monitoring period, health authorities said.

Zeng Qun, deputy head of Shanghai Civil Affairs Bureau, said during a press conference Thursday that the city would strengthen measures for international returnees during their self-monitoring period at home. During the weeklong isolation, such individuals are banned from using public transportation, walking around their neighborhoods, and going to crowded places such as movie theaters and restaurants.

“For the very few violations of the provisions, we will take serious disciplinary measures in accordance with the law,” Zeng said.

On Thursday, Shanghai also reported three asymptomatic infections — such cases are, however, not included in the country’s COVID-19 tally — linked to the same transmission chain. Local health authorities said that four of the five patients were fully vaccinated, although it’s unclear if they had received booster shots.

As one of China’s busiest entry points for international arrivals, Shanghai has a relatively lenient quarantine policy compared with other cities. But health experts have called for strengthening the city’s defense against the virus, as the Omicron variant drives the global COVID-19 surge.

Zhang Wenhong, the infectious disease expert tasked with managing Shanghai’s coronavirus response, said there was an influx of “imported cases” in the city’s dedicated COVID-19 hospital — the highest since the start of the pandemic in 2020.

“We are still at the most difficult time in our battle against Omicron,” Zhang wrote on his Weibo microblogging account on Thursday, though it’s unclear if the local cluster was linked to the highly transmissible variant. “The best strategy for China is to maintain its strategy and be patient … Eventually (we’ll) get through the pandemic with an extremely low death rate and gradually return to normal.”

Amid an uptick in coronavirus cases among passengers who returned from abroad, multiple cities, including Shanghai, have canceled several international flights under the country’s “circuit breaker” policy. Some 70 flights from the U.S. to the Chinese mainland have been canceled this year alone, according to Reuters.

On Thursday, China reported 143 confirmed local COVID-19 cases, with the majority in the central province of Henan and the northern port city of Tianjin. Infections in Xi’an remained in single digits, as the northwestern city entered its fourth week of lockdown.

Editor: Bibek Bhandari.

(Header image: A man photographs the milk tea shop where two employees tested positive for COVID-19 in Shanghai, Jan. 14, 2022. IC)