Northwest China reports 137 asymptomatic COVID-19 cases

China's northwestern region has reported 137 new asymptomatic coronavirus cases, the highest daily number in last seven months, state-run media reported on Monday.

Consequently, health authorities in the region launched a mass drive to test 4.7 million people, according to Global Times.

A 17-year-old female, working in a cloth factory in Kashgar, was first reported as asymptomatic on Saturday.

The city then conducted nucleic acid tests on 831 factory employees, but none tested positive. However, 137 close contacts of the woman's parents were found to be positive, all asymptomatic.

Health experts have termed the situation "serious."

"The situation looks serious... some of the asymptomatic cases could turn into confirmed cases later on," Zeng Guang, chief epidemiologist of the Chinese Center for Disease Control and Prevention, said.

Following the mass infection, major Chinese cities including Beijing and Shulan in northeast China's Jilin province issued travel alerts as a preventive measure.

Shulan ordered people who had been to Kashgar since Oct. 10 to immediately report to local authorities, and be quarantined for 14 days.

China, where the novel virus was first detected last December, has so far reported 85,810 virus cases, including 4,634 deaths and 80,911 recoveries, according to the National Health Commission.

It has largely contained the virus through a series of strict lockdowns and restrictions. Europe, however, is going through a second wave, with many countries introducing curfews and emergency measures to curb the spread of COVID-19.