Airports in Wuhan and Beijing were on heightened alert with additional health screenings on Wednesday as the number of people infected with a coronavirus reached over 400.
Workers in biohazard suits checked passenger's temperatures with thermal devices on a plane that landed in Beijing from Wuhan.
At Wuhan Tianhe International Airport, staff monitored people coming in and pulled aside some for screening by doctors.
The vast majority of travellers donned masks, as did staff, flight attendants, police and soldiers standing watch over the terminal.
Chinese health authorities urged people in the city of Wuhan to avoid crowds and public gatherings, warning that a new viral illness that has infected hundreds and caused at least nine deaths could spread further.
The number of new cases has risen sharply in China, the center of the outbreak.
There were 440 confirmed cases as of midnight Tuesday in 13 jurisdictions, said Li Bin, deputy director of the National Health Commission.
Nine people have died, all in Hubei province, since the outbreak emerged in its provincial capital of Wuhan late last month.
Anxieties grew after Chinese government expert Zhong Nanshan revealed on state television late Monday that the virus can be spread from one person to another.
Authorities previously had not confirmed human-to-human transmission.