The first case of the Omicron variant of the coronavirus in China was recorded in the northern city of Tianjin. The infection comes as the country imposed a zero-tolerance strategy to halt the spread of the virus.

On Monday, Chinese health authorities confirmed that they had detected the Omicron variant in a patient who had returned to the country from abroad. The patient reportedly did not show any symptoms when he arrived in the country. He was confirmed to have been infected on Dec. 9, and it took days before authorities could confirm that he was carrying the Omicron variant.

Authorities said the patient is now being quarantined and observed at a designated hospital. China is currently dealing with a resurgence of new cases of the Delta variant, particularly in its eastern province of Zhejiang. Over the weekend, several companies were forced to halt operations as local governments imposed strict pandemic restrictions.

Omicron infections have already been documented in more than 50 nations since it was originally discovered in South Africa. The mutated coronavirus strain has been labeled a "variant of concern" by the World Health Organization. Boris Johnson claimed on Monday that at least one person in the UK had died from Omicron.

Health experts said if the variant is not adequately handled, it may throw Beijing's pandemic plan into disarray. China's hardline response to the pandemic has provided Chinese residents with a largely virus-free existence since last year, but it has been criticized by certain medical specialists, who suggest that an alternate plan to live with the virus with a significant vaccination rate should be used instead.

The coronavirus was first detected in mainland China. Within months, the government had brought the outbreak under control, but the virus had spread worldwide.

Only a few pockets of infections had remained over the previous 18 months, as China adopted a stringent "zero-tolerance" policy that resulted in immediate community lockdowns and travel restrictions.

On Monday, the mainland health commission reported 51 locally verified cases, 25 of which were related to international tourists but no new deaths.  Most of the new locally transmitted cases with symptoms were detected in Zhejiang.

More than a dozen publicly traded firms halted operations on Monday as a result of the surge in Zhejiang, a manufacturing region and home to the e-commerce behemoth Alibaba. The stock prices of the companies that chose to close down swiftly dropped after they made their announcements.