Washington US health authorities on Tuesday announced the first case of a person on American soil sickened by a new virus that emerged in the central Chinese city of Wuhan, and intensified airport health screenings.
The man, a US resident in his 30s who lives near Seattle, is in good condition, according to federal and state officials.
The man is being "hospitalised out of an abundance of precaution, and for short term monitoring, not because there was severe illness," said Chris Spitters, a Washington state health official.
The news came as Asian countries ramped up measures to block the spread of the new virus as the death toll in China rose to six and the number of cases surpassed 300.
China is about to embark on the Lunar New Year holiday -- a huge travel time for hundreds of millions of people.
The man hospitalised in Washington state had travelled to the US from Wuhan, but did not visit the seafood market thought to be at the heart of the outbreak.
He entered the US on January 15 -- two days before health screenings for those travelling from Wuhan began at airports in Los Angeles, New York and San Francisco -- and approached health authorities himself after reading news reports about the virus.
Officials from the Centers for Disease Control and Prevention (CDC) will now be deployed to two additional international airports, in Chicago and Atlanta.
All travellers on flights from Wuhan, either direct or connecting, will now be re-routed to the five airports with screening systems in place.
Nations across the Asia-Pacific region stepped up checks of passengers at airports to detect the SARS-like coronavirus.
Fears of a bigger outbreak rose after a prominent expert from China's National Health Commission confirmed late Monday that the virus can be passed between people.