South Carolina health officials have declared an end to a measles outbreak that sickened 997 people over six months, making it the largest single-location outbreak in the United States since the disease was declared eliminated.
The outbreak began in October 2025 and spread mainly through largely unvaccinated school-age children, according to the South Carolina Department of Public Health.
The last case was reported on March 15, after which the state health officials waited 42 days - twice the virus's maximum incubation period - before formally declaring the outbreak over.
The U.S. Centers for Disease Control and Prevention worked with state authorities through the response, helping analyse the data.
Of the 997 cases, 932 occurred in people who had never been vaccinated. Spartanburg County accounted for more than 90% of infections, while children aged 5 to 17 made up the largest share, with 639 cases.
The outbreak cost the state an estimated $2.1 million and led to 874 students being asked to quarantine across 33 schools.
Health officials said the response also drove a sharp rise in measles vaccinations, with more than 81,000 doses administered statewide - a 31% increase from 2025.
The outbreak unfolded amid a worsening national backdrop. The United States recorded 2,288 confirmed measles cases in 2025, the highest annual total since 1991, according to the CDC, and reported 1,792 cases this year as of April 23.
Measles was declared eliminated in the United States in 2000, meaning the virus was no longer spreading continuously within the country.
That elimination status is now under review, with the Pan American Health Organisation delaying a decision until November.
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