South Carolina health officials have declared the end of a measles outbreak that sickened nearly 1,000 people, making it the largest in the United States since the disease was eliminated in 2000. The outbreak began in Spartanburg County in October, primarily hitting a close-knit evangelical Slavic community where vaccination rates had dropped to just 89% among school-age children—well below the 95% threshold needed for herd immunity. Twenty-one patients required hospitalization, with some developing severe complications including pneumonia and brain swelling.

The outbreak was contained through a combination of factors: local clinics, pharmacies and doctors administered nearly 4,000 additional MMR doses compared to the previous year, and the virus eventually ran out of vulnerable people to infect. More than 870 students faced quarantine, with some required to stay home for two separate 21-day periods. Even those who avoided infection may face lasting consequences—measles can cause "immune amnesia," wiping out protection children have built against other illnesses, and in rare cases triggers a degenerative brain condition years later.

The state reported a new unrelated measles case in a different region last week, with 34 people potentially exposed. The U.S. recorded a 34-year high in measles cases in 2025 and is on track to surpass that this year, with ongoing outbreaks in Florida and Utah.