Travelers may undergo screenings at airports to control the spread of coronavirus. Research shows that these efforts have little to no effect on slowing the spread of disease.

Harvard’s Marc Lipsitch said evidence indicates that the international cordon keeping coronavirus cases bottled up in China is a leaky one, and it’s likely that the relative handful of global cases reported so far are undercounted. If true, that will lead to widespread illness internationally, including in the U.S.

Harvard epidemiologist Michael Mina said as many as 100,000 people are likely already infected with the new coronavirus, with many more likely to come.