On Tuesday, health officials issued a warning about possible measles exposure in both Dulles and Ronald Reagan airports in the Washington, D.C. Metro area.

The Virginia Public Health Department said they had a “confirmed case” of a person traveling through both airports while coming home from an international trip.

The incident highlights the danger of allowing millions of unvetted foreigners through the southern border.

The latest incident doesn’t appear to be dangerous according to authorities but highlights how dangerous infectious diseases can be when spread at highly mobile locations like airports.