Measles outbreak in South Carolina’s Upstate reaches 789 cases, largest U.S. surge since 2000

In a second-grade classroom on the northern edge of Spartanburg County, nearly half the desks sit empty. The children assigned to them are healthy, but they are not allowed to be here. They are among hundreds of students ordered to stay home for three weeks after being exposed to measles.

Those absences are part of a fast-growing outbreak in South Carolina’s Upstate region that has now sickened 789 people, mostly children, state health officials said Tuesday. It is the largest single measles outbreak in the United States since the disease was declared eliminated nationally in 2000.

The South Carolina Department of Public Health (DPH) said the outbreak, first recognized in October, remains centered in Spartanburg County and neighboring areas. Roughly 88% of those infected are unvaccinated, and state data show the virus has moved primarily through schools and households where immunization rates are far below what is needed to stop transmission.

“Vaccination continues to be the best way to prevent measles and stop this outbreak,” the department said in its latest update.

A record-setting outbreak

On Jan. 27, DPH reported 89 new cases since the previous Friday, bringing the total number of cases linked to the Upstate outbreak to 789. At least 18 people, including adults and children, have been hospitalized for complications. No deaths have been reported.

The outbreak has now surpassed a 2025 measles outbreak in West Texas, which ended with 762 cases. That Texas surge, concentrated in under-vaccinated Mennonite communities, was previously the largest U.S. measles outbreak in decades.

Measles was declared eliminated in the United States in 2000, meaning health officials had interrupted continuous local transmission of the virus for at least 12 months. The current South Carolina outbreak, together with continuing clusters elsewhere, is testing whether that status can be sustained.

How it started — and where it spread

South Carolina reported several sporadic measles cases in Upstate residents in mid-2025, some linked to international travel. All were in unvaccinated individuals. By late September, health officials identified a small cluster in Spartanburg County without recent travel history, signaling local spread.

On Oct. 2, DPH formally declared a measles outbreak in the Upstate region. Early cases were traced to school settings, including an international charter school and local elementary campuses. As the fall term continued, additional schools reported exposures, and the department began posting regular Tuesday and Friday updates, along with lists of public locations where people might have been exposed.

What began as a handful of cases grew steadily through November and December. By early January, DPH reported 310 outbreak-related cases. Eleven days later, the tally had climbed to 646. As of Jan. 27, state officials said 557 people were in quarantine and 20 people with measles were in isolation.

The virus has not stayed within South Carolina’s borders. In Napa County, California, health authorities confirmed their first measles case since 2012 in an unvaccinated child who recently traveled to South Carolina. The child developed symptoms after returning home.

“MMR vaccines are our best defense against the measles virus and its complications,” Dr. Christine Wu, Napa County’s public health officer, said when announcing the case. “Simply being in the same room with someone who has measles can result in infection for people who are not immune.”

Officials in North Carolina, Ohio and Washington state have also reported cases tied to travel from South Carolina or linked outbreaks, according to local and regional public health reports.

Children and unvaccinated communities at the center

Measles is one of the most contagious viruses known. It can linger in the air for up to two hours after an infected person leaves a room and is transmissible for several days before the characteristic rash appears. Public health agencies estimate that 9 out of 10 susceptible people who are exposed will become ill.

In the South Carolina outbreak, those susceptible individuals are overwhelmingly children.

DPH data show that of the 789 cases, 203 are in children younger than 5, and 493 are in children and teenagers ages 5 to 17. Only 65 cases have been reported in adults 18 and older; the age of 28 patients was not yet recorded.

Vaccination status has been documented for most cases. Of those, 695 patients are unvaccinated, 14 received one dose of measles-mumps-rubella (MMR) vaccine, and 20 had received the recommended two doses. Vaccination status is unknown for 60 patients.

Those figures are consistent with the known effectiveness of the MMR vaccine. Two doses are about 97% effective at preventing measles.

Statewide, South Carolina reports high overall childhood immunization rates. But the averages obscure pockets of very low coverage.

The epicenter of the outbreak is a cluster of schools in Spartanburg County and nearby communities, health officials and independent disease researchers say. Many are small private or religious academies where large numbers of students have vaccine exemptions or incomplete records. In some of these schools, reported MMR coverage has been closer to 20% than the 95% level generally needed to prevent sustained measles transmission.

Public schools have also reported exposures and quarantines, particularly in areas where vaccination coverage has lagged. In its Jan. 27 update, DPH listed more than 20 schools with active quarantines, including dozens of students sent home at individual campuses.

The state’s response

South Carolina health officials have launched a multi-pronged response. The state’s outbreak page tracks case numbers, exposure locations and quarantine orders. The department has emphasized that people with possible symptoms should call ahead before going to a clinic or emergency department, to reduce the risk of infecting others in waiting rooms.

Unvaccinated or non-immune students who are exposed at school are being excluded from in-person classes for 21 days after their last exposure, consistent with national guidelines. That has meant weeks of missed instruction for many children.

The department has also deployed a Mobile Health Unit to offer MMR vaccination at or near affected schools and community sites. Vaccines are being offered at no cost through county health departments, doctors’ offices and pharmacies.

“Complications are not reportable to DPH, but we have learned that 18 people, including both adults and children, have required hospitalization for complications of the disease since the beginning of the outbreak,” the agency said Tuesday, underscoring the seriousness of an illness that some families had assumed was rare or benign.

A national backdrop of falling coverage

The South Carolina surge comes amid a broader erosion of childhood vaccination in the United States.

Nationally, measles vaccination rates for kindergarten students have fallen for several consecutive years, according to federal surveillance reports. For the 2023-24 school year, roughly 92.5% to 92.7% of kindergarteners had received the recommended two doses of MMR vaccine, down from more than 95% before the COVID-19 pandemic. Public health agencies say about 95% coverage is needed to reliably prevent outbreaks.

At the same time, the share of children with exemptions to one or more required vaccines has reached record levels, around 3.3% nationwide, with significantly higher rates in some states. Those exemptions — often granted on religious or philosophical grounds — tend to be clustered in particular communities and schools.

In 2025, the United States recorded more than 2,200 measles cases, the highest national tally in more than three decades. Nearly one-third of those came from the West Texas outbreak, which state officials said cost more than $10 million to contain and resulted in two deaths in unvaccinated school-aged children.

Measles elimination status under review

The surge of measles cases across multiple states has drawn international attention.

The Pan American Health Organization, which monitors the status of measles elimination in the Americas, has scheduled a virtual meeting for April 13 with U.S. and Mexican officials to assess whether the two countries still meet the criteria for measles elimination.

Under that standard, a country must show that no single strain of measles virus has spread continuously for 12 months or more within its borders. The presence of imported cases and outbreaks does not by itself end elimination status, but long-lasting chains of transmission can.

Measles was once a routine childhood illness in the United States. Before vaccines were introduced in the 1960s, the disease infected an estimated 3 million to 4 million Americans each year, hospitalizing tens of thousands and killing hundreds of children annually. The introduction of widespread vaccination pushed case counts down to double digits most years and led to the 2000 elimination declaration.

Now, as Spartanburg families juggle quarantine schedules and health workers go door to door offering shots, the country’s success in holding that line is being tested.

In the Spartanburg classroom with the empty desks, the teacher has taped a simple reminder above the whiteboard: “We’ll see you back soon.” When those students return will depend not only on the date on their quarantine orders, but on how quickly their community — and others like it around the country — decide to close the gaps that allowed measles to spread again.