US facing second measles surge this year as outbreak accelerates in South Carolina

By Deidre McPhillips, CNN

(CNN) — As multiple measles outbreaks simmer across the United States, cases are accumulating nearly as quickly as when the West Texas outbreak was at its peak this spring.

There were 84 new measles cases reported in the past week nationwide, according to data posted Wednesday by the US Centers for Disease Control and Prevention. That’s more cases than have been reported in a single week since April, when there was an average of about 100 new cases per week.

Texas hasn’t reported any new measles cases since state officials declared that the outbreak there was over in mid-August.

Now, case counts are growing quickly in South Carolina, where state health officials say more than 250 people are in quarantine after possible exposure and 16 are in isolation because of illness. Some of them are in quarantine for a second time because they did not acquire additional protection — through vaccination or natural immunity from an infection — since the first exposure, state epidemiologist Dr. Linda Bell said at a briefing Wednesday.

“This is a reminder that the maximum incubation period for measles is 21 days, so for any student or anyone to have to go through that quarantine period twice, that’s a significant amount of time,” Bell said. “Vaccination continues to be the best way to prevent the disruption that measles is causing to people’s education, to employment and other factors in people’s lives in our communities.”

And new cases in the state are adding up at an accelerating pace, she said.

Although there is overall good compliance with quarantine recommendations, Bell said that some factors contributing to the concerning “spike” are holiday gatherings, travel and “lower than hoped for vaccination coverage” for a highly contagious virus.

There have been 111 measles cases reported in South Carolina since the outbreak started in October, according to data from the state health department, and at least 105 of those were in people who had never received a dose of the measles-mumps-rubella (MMR) vaccine. Two doses of the vaccine are recommended in childhood and offer 97% protection against measles infection.

Most of the cases are in the upstate region, near Greenville. The state has reported dozens of new cases since Friday, with most coming from an exposure at a church. Exposures have also occurred at schools and medical settings.

“The majority of our cases stem from exposures in known settings. But what we want people to pay attention to is that with each new case in an undervaccinated population, the number of contacts around each new case can spur more and more cases because the disease is so highly infectious,” Bell said. A “similarly rapid increase in vaccination coverage” is important to contain the spread.

Measles cases also continue to accumulate in Utah and Arizona, where an outbreak along the state line has been growing for months. Arizona has reported 176 cases as of Tuesday — second only to Texas this year – while Utah has reported 115 cases.

It’s been a record year for measles in the US. Between January and July, there had been close to 1,300 cases reported, more than in any other year since the disease was declared eliminated in the country a quarter-century ago.

Now, the US has recorded more than 1,900 cases for the year, CDC data shows, and the vast majority have been among people who were unvaccinated. If the outbreaks continue into January, the US is at risk of losing its elimination status, like Canada did last month.

There have been 47 outbreaks in the US in 2025, nearly three times more than there were last year, according to the CDC. An outbreak is defined as three or more cases that are related.

More than 200 people have been hospitalized, and three people — including two children — have died because of measles.

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