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.