Worobey and his co-authors estimated that the infection that started the Seattle area outbreak arrived in the country around Feb. 13, shortly after President Trump’s ban on travel from China went into effect on Feb. 2. Thousands of Americans in the country fled back to the United States in the days after the ban was announced…

When the first case of local transmission was linked back to WA1, it appeared that the efforts to contain his infection hadn’t been adequate. But in fact, they probably were, Worobey said.

“Conclusions that the Seattle area was already six weeks into an epidemic by the end of February, rather than two or three, and the notion that stringent efforts to prevent spread had failed in the WA1 case, may have influenced decision-making about how to respond to the outbreak, including whether such measures were worth the effort,” he and his co-authors wrote.