Genome sequencing makes closing the borders seem quite prudent.
What I'll quote is from FR. The full article has details on genome sequencing and how that technique was used to identify the sources of infection. The details are provided in tweets by Trevor Bedford, who has been a consistently reliable source. Here's FR, which provides a selection of quotes as a synthesis. The statement that President's action was "too late" is, in the complete context, is simply awkward and not intended as a criticism--far from it:
When President Trump restricted travel to and from China nearly two months ago, the outcry from the left was deafening. Everyone from Democrats to the World Health Organization to mainstream media panned the move as racist and xenophobic. Now, information stemming from genome sequencing of those infected indicate the President’s unpopular move was not only correct, but may have happened too late.
This is fascinating, it looks like 90% of the COVID transmission in Seattle is from a single introduction in late Jan from China. The NY intro is from Iran and San Diego intro from Europe. https://t.co/ZBbzrtgU5u
— PoliMath (@politicalmath) March 16, 2020
The Wuhan coronavirus may not be as fatal as it was initially believed, but its spread is far greater than the flu or anything major we’ve seen in decades. This is due in part because asymptomatic people can be contagious for over a week. As the disease spreads across the country and around the world, one political assessment cannot be disputed: The left’s love for open borders has, is, and will continue to exacerbate the problem.
Here's why I call this hopeful and important. The biggest outbreak of Covid-19 is in Seattle. New York comes next. Each can be traced to single persons, if the genome sequencing results are valid. To me, that means that there probably was not an infection process anywhere in the US that involved multiple persons as originators, and that would tend to the conclusion that the spread in the US has been fairly limited. In addition, the fact that the this happened in late January, just before President Trump began instituting border controls, also is a hopeful sign that control efforts--while not fully effective--have been having an effect, since (except for Boston) these are the major outbreaks. It's important for public health officials to know this, and it's a hopeful sign that we will be able to control Covid-19. Not definitive, but hopeful.