The Upstate measles outbreak — at 997 cases, the largest reported in the United States in more than 35 years — has officially ended, the state Department of Public Health announced April 27.
The vast majority of cases, 940, were centered in Spartanburg County, but cases were also confirmed in Greenville, Anderson, Pickens, Lancaster, Cherokee and Sumter counties.
The outbreak began in October last year, and the last confirmed case related to it was reported on March 15. State public health officials cited decreasing measles/mumps rubella (MMR) vaccination rates in recent years as a major driver of the outbreak.
Measles outbreak impacts
That fact is underscored by DPH data on the vaccination status of those who contracted measles during the outbreak which showed of the 997 cases, 932 occurred in people who were unvaccinated.
Other outbreak data points include:
- 264 cases occurred in children aged 5 and under
- 639 occurred in people aged 5-17
- 87 occurred in people 18 or older
- 33 schools in 7 school districts impacted by measles exposures with 874 students asked to quarantine
- More than 1,670 calls made by investigators
- $2.1 million estimated outbreak cost to the state (direct costs for DPH response)
According to DPH, 42 days were required to elapse with no new measles cases reported before the outbreak could be declared ended. That period of time is double the incubation period for measles and provides a clear indication the virus transmission chain has been broken.
Positive signs
One positive development in the face of the outbreak has been a noticeable uptick in vaccination rates during the six months of the outbreak, both locally and across the state, according to DPH.
In Spartanburg County where the outbreak originated and was largely focused, 3,788 more MMR vaccines were administered than the prior year — a 93.6% increase. Across the Upstate, 14,745 more vaccines were administered (82.4% increase), and statewide 81,096 more doses were given (31.3% increase).
The state was also fortunate that despite the magnitude of the outbreak, cases remained largely confined to one county, according to Brannon Traxler, DPH deputy director of health promotion and services and chief medical officer.
Traxler spoke about lessons learned during the final DPH media briefing on the outbreak held April 27.
She said DPH believes the outbreak ended as soon as it did for three main reasons:
- Those infected developed natural immunity
- The vast majority of people infected followed public health directives to isolate and quarantine
- There was a significant increase in the number of people vaccinated during the outbreak, with January and February 2026 seeing record numbers of vaccinations
“The outbreak is over, but our work to understand and prevent measles and future outbreaks is not,” Traxler said. “We believe our outbreak response team did a tremendous job under really unprecedented conditions, but there are always things that we can learn from and improve on … with future responses.”
Traxler said there remain pockets all over South Carolina where populations remain vulnerable to future outbreaks due to low rates of protection from vaccination or natural immunity, and DPH will continue close monitoring for signs of a new outbreak.
Measles cases by county
- Spartanburg — 940
- Greenville — 36
- Anderson — 8
- Pickens — 6
- Lancaster — 4
- Cherokee — 2
- Sumter — 1
