Health officials in South Carolina are warning that the highly infectious measles virus is spreading undetected in communities in the northern part of the state, specifically Spartanburg and Greenville counties.
Last week, officials in Greenville identified an eighth measles case that is potentially linked to the outbreak. Seven outbreak cases had been confirmed since September 25 in neighboring Spartanburg, where transmission was identified in two schools: Fairforest Elementary and Global Academy, a public charter school.
Across those two schools, at least 153 unvaccinated children were exposed to the virus and have been put in a 21-day quarantine, during which they are barred from attending school, state officials said in a press conference. Twenty-one days is the maximum incubation period, spanning from when a person is exposed to when they would develop a rash if infected.
It's unclear how the latest case in Greenville became infected with the virus and how they may link to the nearby Spartanburg cases.
"What this case tells us is that there is active, unrecognized community transmission of measles occurring in the Upstate [northern region of South Carolina], which makes it vital to ensure that the public have received their measles vaccinations," the South Carolina Department of Public Health said in an announcement.
The two recommended doses of the measles, mumps, and rubella (MMR) vaccine are about 97 percent effective at blocking the infection, and that protection is considered lifelong. Without that protection, the virus is extremely contagious, infecting 90 percent of unvaccinated people who are exposed. The virus spreads easily through the air, lingering in the airspace of a room for up to two hours after an infected person has left.
State and national trends
According to state data, both counties linked to the outbreak have low vaccination rates among school children in the 2024–2025 school year. Spartanburg's immunization rate is 90 percent, and Greenville's is 92.4 percent, both well below the target of 95 percent that experts say is needed to prevent community spread.
Spartanburg has the highest rate of religious vaccination exemptions among students in the state, at 8.2 percent. That means that even if all other students get their recommended vaccinations, they would still only have vaccine coverage of 91.8 percent. Neighboring Greenville has a religious vaccination exemption rate of 5.3 percent, with a max of 94.7 percent.
In the past five years, vaccination rates in South Carolina have slipped from over 95 percent to 93.7 percent, while religious exemptions have risen. Both trends have played out across the country as anti-vaccine rhetoric, misinformation, and disinformation have taken hold. The latest data indicates that the MMR vaccination coverage for US kindergartners was just 92.5 percent in the 2024–2025 school year, down from 95.2 percent in 2019–2020. Non-medical exemptions are now at 3.4 percent, an all-time high.
Relatedly, the US is experiencing its highest measles case count in 33 years, stretching several years past when the virus was declared eliminated from the US in 2000. The Centers for Disease Control and Prevention has tallied 1,563 confirmed cases from 41 states this year. Most of the cases are linked to the 44 identified outbreaks. The largest so far occurred in Texas, which has reported 803 cases this year.
Three people, including two previously healthy school-aged children, have died of measles in the US this year.
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