COLUMBIA — The nation’s largest measles outbreak in decades came to an end Sunday, after more than a month without sickening anyone, according to the state health department.

The six-month outbreak infected 997 people, including at least 21 who required hospitalization, according to health department data. No one died.

South Carolina’s was the largest reported cluster of measles cases in the nation in the past 35 years, according to the health department. Officials declared it over after receiving no related reports of new cases in the past 42 days, which is double the virus’ incubation period.

“No one asks to be part of an outbreak, but thanks to the dedication of many South Carolinians, from school and hospital staff, medical providers, faith-based groups, the (Department of Public Health) team, businesses, and families working together, we have overcome this outbreak,” interim public health director Ed Simmer said in a statement Monday.

Health officials did diagnose one person in Saluda County during the 42-day window, the health department said April 17, but officials determined the case was separate from the larger outbreak in the Upstate. That person had recently returned from a trip abroad, according to the department.

The outbreak primarily affected unvaccinated children in Spartanburg County.

Of those sickened, at least 93% had not received either of the vaccine’s two doses. Spartanburg County residents accounted for 94% of cases, and 90% were under the age of 18, according to health department data.

Health officials credited the end of the outbreak to increased vaccination rates, a high number of people obeying quarantine orders and staying home after exposure and the natural immunity people infected with the virus received.

Although people infected gain a barrier of protection against future infection, it comes with significantly higher health risks than vaccination and preventing the disease outright, said Brannon Traxler, the agency’s chief medical officer.

Short-term cases can lead to pneumonia or encephalitis.

And in rare cases, measles can cause complications that don’t surface for years, such as fatal brain disorder called subacute sclerosing panencephalitis. Measles can also cause “immune amnesia,” erasing the body’s knowledge of how to fight certain infections, according to the public health agency.

The health department did not track the severity of cases, so it’s unclear how often these issues arose. But even in mild cases, those infected likely spent days to weeks dealing with a loss of appetite, low energy and the disease’s characteristic rash, Traxler told reporters Monday.

“They just didn’t feel well,” Traxler said of those infected. “I don’t think anyone wants to see their children suffering, and that is very much a component that is not captured by pure numbers.”

Altogether, the state spent an estimated $2.1 million on staffing and vaccine costs. Public health employees worked 30 weeks straight, including through the winter holidays, and hosted free vaccine clinics for the Upstate, Traxler said.

“Ending this outbreak was a monumental effort” for the department, she added.

Beyond just the health care costs the outbreak may have had other impacts, such as parents taking off work to care for sick children or quarantining themselves, as well as the effect on businesses where exposures occurred.

How did we get here?

Officials considered measles eliminated in 2000, 37 years after the introduction of the vaccine. But the past two years brought a national surge in the highly contagious virus as vaccination rates, especially among children, fell.

In South Carolina, the rate of students who received all their vaccines before starting school dropped in recent years, from more than 98% a decade ago to 94% during the 2024-2025 school year, according to state health department data.

The vaccination rate for school children in Spartanburg County, the outbreak’s epicenter, was even lower than the average. Just under 90% of students were fully vaccinated during the most recent school year, according to the data.

Although state law requires all students at private and public schools be up to date with immunizations, families can apply for exemptions for religious or medical reasons. More students have received religious exemptions in recent years, especially after students returned to school following the COVID-19 pandemic.

More than 8% of Spartanburg County’s students had a religious exemption in the 2024-2025 school year, surpassing every other county in the state. While a medical exemption requires a doctor’s note, a religious exemption requires only a parent’s signature and notarization.

A panel of senators rejected a bill last month that would have eliminated these religious exemptions.

In all, nearly 900 students in 33 schools across seven districts missed weeks of school as they quarantined because of exposure to the measles from classmates, according to the department.

Cases surged in January, when winter break made tracking down exposures to confirmed cases more difficult, officials said at the time.

Since the beginning of the outbreak, vaccinations against measles increased statewide, Traxler said.

Spartanburg County residents received nearly 4,000 more doses of the measles, mumps and rubella vaccine during the past six months than they did during the same period the year before, according to health department data.

“I genuinely believe that everyone out there is trying to do what’s best and trying to make the best decisions for their children,” Traxler said. “I’m a parent myself. I understand the struggles that we all go through, just trying to decide, in each and every decision for our children, what is going to give them the best opportunity for the future.”

In addition to schools, many cases also spread from churches.

Among those were churches that held services spoken in Ukrainian and Russian.

With that in mind, the health department made a concerted effort to reach people in those communities, Traxler said.

People who have fled their countries, often because of the government, may be skeptical of any sort of government-led program, Traxler said. Or they may not have access to information about the vaccine or how to get it.

“They have a reason to have the doubts that they do,” she said. “So, then it’s providing that respect, that lack of judgment, and building trust.”

Health officials translated vaccine information into Ukrainian and Russian, and they visited Upstate churches to work with faith leaders and get correct information to people who needed it, Traxler said.

How many of their attendees were among the diagnosed is publicly unknown. The department did not release demographic information on those infected beyond their age and the county where they lived.

What happens next?

Now that the health department has declared the outbreak ended, it is reviewing data, looking for anything it could have done differently or detected earlier, Traxler said.

For one, the department could have done more to monitor hospitalizations and outcomes of cases, rather than only tracking diagnoses, Traxler said.

“The outbreak is over, but our work to understand and prevent measles and future outbreaks is not,” she said.

And while individual measles cases are still likely to pop up from international travel, the department’s primary goal is to keep those cases from expanding into another outbreak, Traxler said.

A large part of that effort will involve continuing to increase the rate of people vaccinated.

Most people receive two doses of the vaccine between the ages of 1 and 6, which protects against about 97% of infections. Most adults do not need booster shots, but anyone who hasn’t gotten both shots should consider doing so, Traxler said.

“Although I hope we do not have another outbreak, if we do, I am convinced South Carolina is well prepared,” Simmer said in a statement. “As we learned from this response, South Carolinians are strong, we are resilient, and when challenged, we rise to the occasion and are better, together.”