A new coronavirus that has spread to almost 2,000 people is infectious in its incubation period – before symptoms show – making it harder to contain, Chinese officials say.
Some 56 people have died from the virus. Health minister Ma Xiaowei told reporters the ability of the virus to spread appeared to be strengthening.
Several Chinese cities have imposed significant travel restrictions.
Wuhan in Hubei, the source of the outbreak, is in effective lockdown.