A months-long measles outbreak in South Carolina has ended, officials announced on April 27.
The last confirmed case related to the outbreak was reported on March 15. Officials had said that if 42 days elapsed without at least one new case linked to the outbreak, they would declare it over.
The period of time is double the length of the incubation period and is a clear indication that the transmission chain has broken, according to the South Carolina Department of Public Health.
Some 997 cases were ultimately linked to the outbreak, which started in mid-2025 in upstate South Carolina and primarily remained within Spartanburg County.
Officials had employed a strategy focused on ramping up vaccinations in conjunction with isolating individuals with confirmed cases until the infectious period passed.
They also traced people who were exposed to measles and encouraged them to quarantine for 21 days after their exposure to monitor for the development of symptoms.
Dr. Brannon Traxler, chief medical officer for the state Department of Public Health, said during a briefing on April 22 that multiple factors were contributing to the winding down of the outbreak, including an increase in vaccinations and the state’s work with tracing the contacts of people who were exposed and encouraging them to quarantine.
“I think those all together basically put … a firebreak ring around it and were able to stop it from spreading,” she said.
Dr. Edward Simmer, the department’s interim director, thanked South Carolinians in an April 27 statement.
“Today, as we declare an end to the Upstate measles outbreak, the largest reported in the United States in more than 35 years, I wish to humbly and profoundly thank the many South Carolinians whose hard work prevented this outbreak from becoming far larger and more serious than it could have become,” he said. “I am very thankful for their efforts and support during this challenging time.”
Without the efforts, the outbreak would have been much larger, Simmer said.
Of the 997 people who were infected, 932 had not received a measles vaccine, according to the state. Forty-six had received at least one dose of a measles vaccine. The remaining people had unknown vaccination status.
The Centers for Disease Control and Prevention played a role in responding to the outbreak, including providing funds for vaccines.
Sen. Tim Scott (R-S.C.) told Health Secretary Robert F. Kennedy Jr. during a recent hearing that the CDC “did truly an incredible job helping South Carolina, my home state, throughout our measles outbreak.”
South Carolina also received assistance from the CDC Foundation and Clemson University, state officials said.
Separate outbreaks are ongoing in several states, including Utah.
There were 2,288 confirmed measles cases recorded in the United States in 2025, the most since 1991. Through April 23, there had been 1,792 confirmed cases across dozens of states.