Vaccination eliminated measles from the U.S. 25 years ago. But it can still spread in pockets where vaccination rates are low, like the west Texas county with a current outbreak. Here's how fast.

When the local hospital warned of a brewing measles outbreak, Kaleigh Brantner urged fellow residents of this rural West Texas community to beware of vaccinating their children. Two weeks later, her unvaccinated 7-year-old son came home from school with a fever.