Two cases of the coronavirus have been "confirmed" in France, the first in Europe, French Health Minister Agnes Buzyn said on Friday.
The first case involved a patient in hospital in the southwestern city of Bordeaux while the other was in Paris, the minister told reporters.
Both had recently travelled to China and had now been placed in isolation.
"We are in the process of tracing the history of these patients who have tested positive in order to get in touch with the people they have been in contact with," Buzyn said.
"We have today the first European cases probably because we developed the test very quickly and we are capable of identifying them.
The first patient, 48, returned to France on January 22. The patient, described as "well", had "passed through Wuhan", the Chinese city at the centre of the deadly outbreak, and was hospitalised on Thursday in Bordeaux.
"We know that since the patient has been on French soil they have had contact with a dozen people, we are going to contact them."
She said she had only just received information on the second case and was not yet in a position to make it public.
"You have to treat an epidemic as you treat a fire, quickly to locate the source" and "contain it as quickly as possible," Buzyn added.
The previously unknown virus has caused alarm because of its similarity to SARS (Severe Acute Respiratory Syndrome), which killed hundreds across mainland China and Hong Kong in 2002-2003.
The outbreak emerged in late December in Wuhan, an industrial and transport hub of 11 million people in China's centre, spreading to several other countries including the United States.
To date the death toll stands at 26.