US: South Carolina measles cases jump by nearly 100

The South Carolina health department on Friday reported 310 measles cases related to the ongoing outbreak in the state, an increase of 99 since earlier this week and marking their sharpest rise in the months-long surge.

The widening outbreak in Upstate South Carolina, located in the northwest part of the state, remains centered around Spartanburg County, the South Carolina Department of Public Health said.

“This is the sharpest increase we’ve seen since the start of the outbreak in October,” the state health department spokesperson told Reuters in an email.

Of those infected, 256 were unvaccinated, two were partially vaccinated with one of the recommended two-dose measles-mumps-rubella vaccines, two were fully vaccinated and 50 had unknown vaccination status.

Most cases were reported in children in the age group of five to 17 years, followed by those below five years of age.

There are currently 200 people in quarantine and nine in isolation. The latest end of quarantine for them is January 29, the state health department said.

“The number of those in quarantine does not reflect the number actually exposed,” said Linda Bell, state epidemiologist.

“An increasing number of public exposure sites are being identified with likely hundreds more people exposed who are not aware they should be in quarantine if they are not immune to measles,” Bell said.

The Centers for Disease Control and Prevention reported a total of 2,144 measles cases in the United States in 2025.

The World Health Organization is expected to make a call this year on whether the United States keeps its measles elimination status.

To be considered measles-free, a country must stop the spread of the virus and be free of locally transmitted cases of the same strain for 12 months or longer, in addition to having high-quality surveillance systems.