Airports around the country were thrown into chaos Saturday night as workers scrambled to roll out the Trump administration’s hastily arranged health screenings for travelers returning from Europe.

Scores of anxious passengers said they encountered jam-packed terminals, long lines and hours of delays as they waited to be questioned by health authorities at some of the busiest travel hubs in the United States.

The administration announced the “enhanced entry screenings” Friday as part of a suite of travel restrictions and other strategies aimed at slowing the spread of the coronavirus. Passengers on flights from more than two dozen countries in Europe are being routed through 13 U.S. airports, where workers check their medical histories, examine them for symptoms and instruct them to self-quarantine.

But shortly after taking effect, the measures designed to prevent new infections in the United States created the exact conditions that facilitate the spread of the highly contagious virus, with throngs of people standing shoulder-to-shoulder in bottlenecks that lasted late into the night.