Many local authorities have in recent days reported cluster-infected novel coronavirus cases, underlining a high-risk phenomenon in the spread of the virus.

Cluster-infected cases refer to more than two confirmed patients being found in a small area, like in a family, classroom or workplace, and the infection probably happens because of close contact or common exposure. Such cases highlight how aggregated populations facilitate wide spread of the virus, posing a challenge to epidemic control.

Although the authorities have extended the Spring Festival holiday and delayed the date by which people should return to their place of work to avoid large-scale migration and aggregation of people at the workplace, many provinces and regions have reported a large number of cluster-infected cases, mainly because of families and friends gathering during the Spring Festival holiday.

By Sunday, Beijing had 41 confirmed cluster-infected virus cases involving more than 120 people, which was more than half of the total number of confirmed patients in the capital.

At the same time, Shandong province confirmed 60 cluster-infected cases; 49 involving family gatherings; six involving colleague gatherings; and five from collective exposure. Every infected person in a cluster infects 2.15 other people on average.

One of the patients in a cluster-infected case in Anhui province was just eight months old.

As more such cases come to light, the public should take effective measures to reduce gatherings of people for the sake of their health and that of others.

As the Spring Festival holiday comes to a close and a large-scale rush to return to work sets in, the probability of cluster-infected cases shifts from family gatherings to migrations and workplace gatherings.

Local authorities should be aware of the risks of aggregating people and take effective measures to reduce cluster-infected cases. One way could be by enhancing health inspection in public transport and encouraging enterprises to launch work-from-home options.