The U.S. is facing a second increase in measles this year after an outbreak in South Carolina

As multiple measles outbreaks continue to grow across the United States, cases are piling up almost as quickly as the West Texas outbreak peaked this spring.

Nationwide, 84 new measles cases were reported last week, according to data posted Wednesday by the U.S. Centers for Disease Control and Prevention. That’s more cases than have been reported in a week since April, when there were about 100 new cases per week.

State officials have reported no new cases of measles since Texas declared the outbreak over there in mid-August.

Now, case counts are rising rapidly 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 the illness. Some of them are in quarantine a second time because they did not receive additional protection — through vaccination or natural immunity from infection — from the first exposure, state epidemiologist Dr. Linda Bell said at a briefing on Wednesday.

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

And new cases are adding up rapidly in the state, she said.

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

111 measles cases have been reported in South Carolina since the outbreak began in October, according to state health department data, 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 provide 97% protection against measles infection.

Most of the cases are in the upstate area near Greenville. The state has reported dozens of new cases since Friday, most from exposure at the church. Exposure has also occurred in schools and medical settings.

“Most of our cases arise from exposure in known settings. But we want people to be aware that with each new case in an unvaccinated population, the number of contacts around each new case can trigger additional cases because the disease is so contagious,” Bell said. “A similarly rapid increase in vaccination coverage” is critical to the spread.

Measles cases are also piling up 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.

This is a record year for measles in the US. Between January and July, there were nearly 1,300 cases reported, more than in any other year since the country was declared eradicated a quarter of a century ago.

Now, the U.S. has recorded more than 1,900 cases for the year, CDC data shows, and most were among unvaccinated people. If the outbreak continues into January, the US risks losing its eradication status, as did Canada last month.

There are 47 outbreaks in the U.S. in 2025, nearly three times as many as last year, according to the CDC. An outbreak is defined as three or more related cases.

More than 200 people have been hospitalized, and three people – including two children – have died from measles.

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