With the flurry of COVID-19 cases coming out of the White House, experts have been calling for classic contact tracing to identify who else might be at risk. But these investigations could go even further by adding a technique called viral genome sequencing. Popular among disease detectives, this could answer when and how President Donald Trump himself was exposed.

Much of the focus has been on a September 26 event in the Rose Garden, where the president announced his nomination of Judge Amy Coney Barrett for the vacancy on the Supreme Court. The gathering has been described as a superspreader event, as at least a dozen guests have reported testing positive since. A debate has flared over whether the