As the Spring Festival holiday nears its end and more people embark on their journeys back to cities, health authorities in China said people should avoid going to crowded places and disinfect their homes after confirmed asymptomatic coronavirus cases were reported in several places.

Li Xingwang, chief infectious diseases expert at Beijing Ditan Hospital, confirmed in a news conference in Beijing that asymptomatic cases of the virus have been found in the country, which have increased difficulties in fighting the virus.

In rare cases, the infected people show no symptoms, but test positive for the novel coronavirus, according to Wu Zunyou, chief epidemiologist at the Chinese Center for Disease Control and Prevention. "In such cases, the asymptomatic sufferer can still infect others."

Most of these sufferers can recover on their own without treatment.

Nanjing, Jiangsu province, reported two confirmed asymptomatic virus cases－cases in which the patient shows no symptoms－on Wednesday. The two people, together with another person of their family who showed symptoms, have been sent to one of the city's hospitals designated for treating pneumonia caused by the virus.

The local health department has disinfected the environment and garbage at the community they lived in. It also ordered all 14 families that lived in the same building with the infected family to stay at home for medical observation.

All people living in the community have been given notice of the health risk. Community workers will provide food and other daily necessities to people under observation.

Chaoyang, Liaoning province, reported one confirmed asymptomatic case on Thursday. A doctor treated a patient on Jan 23 and 25.The patient, from Wuhan, had claimed that she came from Sichuan province.

The local center for disease control and prevention found that the doctor had close contact with the patient on Wednesday and confirmed that she showed no symptoms. The doctor is under medical observation in a hospital designated for treating pneumonia caused by the virus.

Wu Jinglei, director of Shanghai Health Commission, said that the commission is paying close attention to asymptomatic cases and adjusting its prevention strategies.

"The transmission of the virus will be more complicated if asymptomatic cases are confirmed," he said, adding that people should wash hands frequently, avoid going out and disinfect their environments.

A doctor surnamed Ma from the Nanjing Center for Disease Control and Prevention agreed that asymptomatic cases may be more of a concern.

"Take the two Nanjing cases for example. One of the two traveled and stayed in Wuhan for several days, and the other was a close contact. The respiratory tract specimen of those people showing no symptoms tested positive for the virus,"Ma said.

In symptomatic cases, "hospitals will scrutinize close contacts, so it's not necessary for the public to take novel coronavirus tests," the doctor said.

He reiterated that close contacts must stay at home for medical observation, avoid contact with other people, wear face masks and open windows for ventilation.