Pennsylvania measles outbreak reaches 1,004 cases across 39 counties, largest in U.S. in three decades
The Pennsylvania Department of Health confirmed 1,004 measles cases across 39 counties in 2026, surpassing South Carolina's 997 cases earlier this year to become the largest U.S. outbreak in three decades. Health officials continue urging vaccination, which is 97% effective after two doses, as they brace for potential further spread beyond the outbreak's center.
