A librarian in Central China's Henan province tested positive for the novel coronavirus on Saturday after being in close contact with two friends who later also tested positive for the virus; neither of whom had any symptoms.

This has brought to people's notice the question of how asymptomatic infections can be tracked and what are the chances of such virus carriers spreading the virus to others.

Experts have their different views about such cases. Some say there are not many such cases, and some say that there is no evidence such cases can spread the virus to others. Others warn that attention must be paid to such cases lest they give rise to another wave of infections.

Given the huge cost that has been paid and the great sacrifices people have made for what has been achieved in containing the spread of the virus in the past more than two months, due attention must be given to asymptomatic cases.

It is true that such cases are not easy to discover and it is quite likely that those who carry the virus without symptoms do not even know themselves that they are infected. But it is important for the government to do whatever it can to track down such cases. For example, all residents in areas that have had high rate infections should be tested to see if there are any asymptomatic cases. Those who have close contact with infected people but without symptoms should be encouraged to register and be tested for the virus.

It is encouraging that the central government has pledged to scale up screening of asymptomatic patients and expand testing to close contacts of infected patients.

Such preemptive efforts are necessary since the possibility exists that there are and they might.

Since there is far from enough known about this new virus, it is urgent to discover as many asymptomatic cases as possible and place them under medical observation, which may provide medical experts with clues to how the virus affects some people worse than others.

As far as the prevention and control work is concerned, either with or without new confirmed cases for a locality, social distancing must be strictly observed and face masks must be worn in public places or when meeting others.

Strict prevention and control measures to detect and isolate asymptomatic cases are essential if the good work that has been done so far is not to be undone.