AP Health officials in South Carolina confirmed 124 new measles cases since Friday, as the outbreak in the northwestern part of the state balloons following the holidays.
There is a second, separate measles outbreak along the Arizona-Utah border, where 418 people have been infected since August.
Last year was the nation’s worst year for measles spread since 1991, according to the Centers for Disease Control and Prevention. The U.S. confirmed 2,144 cases across 44 states. Three people died, all of them unvaccinated.
Measles is caused by a highly contagious virus that’s airborne and spreads easily when an infected person breathes, sneezes or coughs. It is preventable through vaccines and has been considered eliminated from the U.S. since 2000, though the country is at risk of losing that achievement.