On Friday, France confirmed the first three cases of the virus in Europe - all Chinese nationals - with two patients hospitalized in Paris and the other in Bordeaux.
In China, 41 people have died from the virus and more than 1,400 people have been infected globally, including four in Australia and three in Malaysia.
The two patients in Paris are a Chinese couple who arrived in France on Jan. 18, but did not show symptoms until Jan. 19 and 23 respectively, officials said.
"They showed no symptoms when they boarded their plane," Yazdan Yazdanpanah, head of infectious diseases at Paris hospital Bichat told reporters.
The third patient in Bordeaux, a 48-year old Chinese man who works in the French wine industry, had taken a plane from Wuhan to the Netherlands and entered France from there, SOS Medecins medical service in Bordeaux said.
Health Minister Agnes Buzyn told reporters the man had entered France on Jan. 22, had first consulted a doctor about his symptoms on Jan 23, with the virus confirmed Jan 24.
The delayed appearance of symptoms and the entry via a third country underline the limits of screening passengers arriving from China in airports.
Airports in several countries are using scanners to take the temperature of passengers arriving from China but France so far is not doing this.
In Paris, there was a rush to buy face masks and several pharmacies said they were sold out.
"It has been like this since this morning, some people are hysterical," said a pharmacist in Paris.The French foreign ministry said on Friday that it had informed French citizens in Wuhan that it planned to set up a bus service to help them leave.