Today, the Centers for Disease Control and Prevention (CDC) confirmed 172 new measles cases for 2026, increasing a skyrocketing outbreak to 588 infections so far. And the largest outbreak in the country, in South Carolina, which started in October, has grown by 58 cases in three days, reaching 847 cases.
Last year, the CDC confirmed 2,267 cases, the most since 1991. Projecting 588 cases a month for 2026 would mean more than 7,000 total cases, though the rate of illnesses could ebb and flow as the year progresses. Last year, the country topped 600 measles cases in early April.
The huge influx is happening at a time when a top CDC official expressed little concern that the United States is on track to lose the measles elimination status it gained in 2000. Last week, Ralph Abraham, MD, the CDC’s principal deputy director, said losing elimination status is the “cost of doing business” as he emphasized “personal freedom” over vaccination, despite the wide availability of a highly effective vaccine.
Abraham also wrongly tied elimination status to international travel, despite the fact that it solely has to do with locally acquired cases.
CDC reports first outbreaks that began in 2026
After confirming 49 outbreaks in 2025, the CDC today noted the first two of 2026, involving eight patients total. The vast majority of the 588 cases are tied to outbreaks that started in 2025 and continue to expand this year. The CDC defines an outbreak as three or more related infections.
Of the 588 cases this year, 94% (550) are outbreak-related. And only three are travel-related. The remaining 585 locally acquired cases were reported by 17 states.
Among patients, 27% are 5 years and younger, and 85% are in those 19 years and younger. The percent of measles patients 20 and older has dropped from 30% in 2025 to 11% so far this year. Ninety-three percent of case-patients were unvaccinated or have an unknown vaccine status.
Three percent have been hospitalized, down from 11% in 2025.
The CDC notes that the measles, mumps, and rubella (MMR) vaccine is very safe and effective. MMR vaccination coverage among US kindergartners, however, has dropped from 95.2% in the 2019-20 school year to 92.5% in the 2024-25 school year, leaving about 286,000 US kindergartners at risk this school year.
The number of public exposure sites indicates that measles is circulating in the community.
In its update today, the South Carolina Department of Public Health (SCDPH) reported 847 measles cases in its outbreak, which is centered in the Upstate region, notably in Spartanburg County. That’s 58 more than on January 27, when the outbreak officially surpassed the 2025 West Texas outbreak as the largest in the country. Cases have surged in recent weeks (see the SCDPH graph at left).
The health department said, “The majority of cases are close contacts of known cases. However, the number of public exposure sites indicates that measles is circulating in the community, increasing the risk of exposure and the risk of infection for those who are not immune due to vaccination or natural infection.”
The SCDPH said the latest exposure site is a Burger King in Roebuck, located in Spartanburg County. Of the 847 cases, 813 (96%) have been in Spartanburg County.
In addition, Idaho now has 21 measles cases in 2025 and 2026, with seven of them in 2026, per an update from the Idaho Division of Public Health this week.
Report spotlights travel-related transmission
Colorado scientists emphasize getting the MMR vaccine after detailing an 11-case measles outbreak late last spring tied to an international traveler. The report also documents how readily the disease spreads on an airplane.
Reporting in the CDC’s Morbidity and Mortality Weekly Report, the researchers—from the CDC and Colorado state and local public health departments—describe how a traveler who contracted measles in the United States traveled internationally, then returned to the country while still contagious, directly infecting at least nine other people.
Four of the 11 patients were hospitalized.
The CDC notified Colorado state health officials on May 20, 2025, of a measles case involving an unvaccinated, non-Colorado resident who had arrived in Denver, Colorado, on an international flight and traveled through Denver International Airport while infectious. The person—the index patient—had measles symptoms on the return trip to Denver.
Officials confirmed nine additional measles cases in Colorado, all but one involving adults. Four of the nine secondary case-patients in Colorado had received two doses of the MMR vaccine.
The first confirmed secondary case involved an unvaccinated young child sitting more than two rows from the index patient. Two other cases involved fully vaccinated adults seated within two rows of the index patient. A fourth flight-related case occurred in a vaccinated person who was seated five rows from the index patient, illustrating how well the virus travels through the air.
Two measles, mumps, and rubella (MMR) vaccine doses are 97% effective in preventing measles.
Five additional cases were tied to exposure to the index patient at Denver International on May 13 or 14. The report notes that “other jurisdictions” (ie, not Colorado) reported seven additional cases tied to this outbreak. The final case was classified as “tertiary,” meaning a case arising from contact with one of the secondary case-patients.
The study authors note, “Measles is a highly contagious vaccine-preventable disease. Two measles, mumps, and rubella (MMR) vaccine doses are 97% effective in preventing measles.”
They add, “During this investigation, testing of urine specimens enhanced case finding, especially among vaccinated persons, who might have experienced milder symptoms and potentially received a negative measles IgM test result.” Two patients who received negative polymerase chain reaction test results from nasal swabs tested positive via urine sampling.
