Post-holiday vigilance must be heightened

That Baise in the Guangxi Zhuang autonomous region reported 98 positive cases after finishing citywide nucleic acid testing on Sunday noon, and another 87 cases are awaiting re-examination for final confirmation of whether they are positive or not, should serve as a wake-up call not just to the authorities but to society as a whole that the virus will seize the opportunity of the holiday travel to spread if given the slightest chance.

The city, home to 3.57 million people and a border port to Vietnam, was locked down on Monday, a necessary move to avoid spillover. Now is time for the localities, especially the rest of Guangxi and neighboring Guangdong province, where most migrant workers from Guangxi earn their livings, to trace the close contacts and sub-contacts of the infected persons over the past three weeks at least－since experts warn that the cluster transmissions might have been going on in Baise for a week or so－to cut the transmission chains and verify the origin as soon as possible.

As such, the epidemiological investigation would have to span a period that started in mid-January, two weeks before the Spring Festival holiday began. That involves almost the whole population movement in the Pearl River Delta region, one of the most robust growth engines and densely populated regions in the country, during the peak travel season.