South Carolina Measles Outbreak Accelerates, Driving Hundreds Into Quarantine

Key Points

Health officials in **South Carolina report a rapidly accelerating **measles outbreak in the Upstate region, centered around Spartanburg and Greenville counties. As of this week, at least 111 cases have been confirmed in the ongoing outbreak.
Measles is an extremely contagious airborne virus that can spread through respiratory droplets and linger in air for hours, especially affecting unvaccinated individuals.
Most of the cases in South Carolina have occurred among people who were not vaccinated against measles, and local vaccination coverage in school-age children remains below the 95% threshold typically needed for community immunity.
Approximately 254 people are currently under 21-day quarantine, many of them students who were exposed at school or community events. Some students are now in a second 21-day quarantine period due to ongoing transmission.
Mobile health clinics have been deployed to offer the measles-mumps-rubella (MMR) vaccine, but uptake has been low among residents.
This outbreak is part of a much larger national resurgence of measles in 2025, with nearly 1,900 cases reported across more than 40 states this year.

Background & Context

Measles was declared eliminated in the United States in 2000 due to high vaccination coverage, but recent years have seen a resurgence of the virus, particularly in communities with low immunization rates. Declining vaccination coverage—reported around 90–90.5% in parts of Upstate South Carolina—has made local populations vulnerable to outbreaks.

Across the U.S. in 2025, measles cases have reached their highest levels in decades, with routine surveillance data showing more than 1,800 confirmed cases so far. The vast majority (over 90%) occurred in unvaccinated individuals.

Why Quarantines Are Happening

Health officials are imposing 21-day quarantines for individuals who were potentially exposed because:

Measles can take up to 21 days for symptoms to appear after exposure.
Infected individuals can spread the virus before symptoms begin.
Quarantining exposed but not yet symptomatic people helps prevent further spread.

Schools and community organizations have had to extend quarantines as new exposures occur, which has been disruptive to education and daily life.

Vaccination Importance

Public health experts emphasize that the MMR vaccine remains the most effective defense:

Two doses are about 97% effective at preventing measles.
A coverage level of around 95% or higher is needed in a community to maintain “herd immunity” and prevent outbreaks.

Officials continue to urge families to ensure their vaccination records are up to date to curb transmission.