- The man is originally from Wuhan and returned to the US on January 15, two days before health officials began screening passengers.
The United States on Tuesday announced its first case of a new virus that has claimed six lives in China and sickened hundreds, joining countries around the world in ramping up measures to block its spread.
The man, a US resident in his 30s who lives near Seattle, is in good condition, according to federal and state officials, and approached authorities himself after reading about the SARS-like infection in news reports.
He is "currently 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.
"This is an evolving situation and again, we do expect additional patients in the United States and globally," added Nancy Messonier, a senior official at the Centers for Disease Control and Prevention (CDC). She stressed that the overall risk to Americans remained low.
The man is originally from Wuhan and returned to the US on January 15, two days before health officials began screening passengers at major airports arriving from the central Chinese city, which is at the heart of the outbreak. The efforts are to be extended now to a total of five US airports.
He lives alone and will be monitored in isolation for at least 48 more hours.
The development came as countries intensified their efforts to stop the spread of the pathogen -- known by its technical name 2019 Novel Coronavirus -- as the number of cases surpassed 300, raising concerns in the middle of a major Chinese holiday travel rush.
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.
That conclusion is shared by the CDC, which said "person-to-person spread is occurring, although it's unclear how easily the virus spreads between people."
The World Health Organization (WHO) will hold an emergency meeting Wednesday to determine whether to declare a rare global public health emergency over the disease, which has also been detected in Thailand, Japan and South Korea and Taiwan.
Many experts believe the US case, while not surprising given the frequency of international flights, makes such a declaration all the more likely.
Mark Woolhouse, a professor of infectious disease epidemiology at the University of Edinburgh, said more evidence was needed to determine if it spreads through the air or via close human-to-human contact.
"It is important to stress that, though similar, it is not as severe an infection as its predecessor, the SARS coronavirus," he added.
- Holiday rush -
Early on, many patients had some link to a Wuhan seafood market where live animals were sold, suggesting an animal-to-person spread.