看美国人怎么说， 防无可防美国case- in 30th， very healthy， no symptoms https://www.heraldnet.com/news/new-virus-from-china-reaches-us-and-snohomish-county/ 重点 At that time he showed no symptoms, health officials said. “In this case, we don’t believe even if we had active screening at the airport that this patient would have been picked up, because at the time we don’t believe the patient had any symptoms of the fever,” said John Weissman, the Washington state secretary of health.