In the 24 hours of Saturday, the city of Beijing reported five confirmed local cases and an asymptomatic one.

On the same day, northeastern Liaoning province registered seven confirmed local infections and three asymptomatic ones.

The numbers seem small, and minor local upticks are nothing new. But the scattered nature of these latest cases, especially when coupled with the difficulty in source tracing, make it even more necessary for tightened control and preventive measures.

That so many — yes, six are indeed many for Beijing, which hasn't seen local infections for months — local infections were detected on one single day in Beijing is unusual. So the city must spare no efforts to trace the source with big data and intensify its preventive measures to make sure that all close contacts are screened.

There is no secret to the country's early-stage success in stemming the virus' domestic spread. It was by and large efficient source-tracing plus timely intervention.

Things might be very different should where and how the victims contracted the virus remain unknown. So while efforts are made to trace the sources of the infections, parallel ones are needed to protect the broader populace.

That is why, several communities of different sizes in Beijing have seen their COVID-19 risk levels raised to "medium" overnight, and community-wide nucleic acid tests being conducted. At the same time, the municipal authorities, while ordering public transport as well as public facilities to operate at reduced capacities, are calling on local residents to avoid unnecessary trips outside the city. Shanghai, too, has urged local residents to refrain from traveling as much as possible to facilitate pandemic control.

Spring Festival, or Lunar Chinese New Year, falls only six weeks after New Year's Day, and the official chun yun, special transport arrangements for the Spring Festival travel rush, will begin soon. The most spectacular annual human migration on earth, mostly from places of work to hometowns, will be a greater challenge for pandemic control.

Since the new cases are still limited to individual localities, and most of the country remains safe, there is no reason to categorically call off either the chun yun or festival celebrations. But it would be most desirable if residents of the places where new infections of unidentified sources are reported avoid unnecessary travel. We have seen cases where asymptomatic virus carriers unknowingly conveyed it to public places.

The national epidemic containment leadership has called for every possible effort to prevent a large-scale rebound of the virus. The related restrictions may affect the way we celebrate the most important festival of the year. But they are necessary for our collective safety.