According to the Centers for Disease Control and Prevention (CDC), by December 30, a total of 2,065 measles cases had been confirmed across 43 states. The CDC’s data reveals that 49 distinct outbreaks were recorded throughout the year, underscoring the urgent need for increased vigilance and preventive measures.

This alarming surge in cases represents the highest number since 1992, a time when the standard practice of administering two doses of the measles-mumps-rubella (MMR) vaccine to children had not yet been established. That year, the nation witnessed 2,126 confirmed measles infections.

Measles remains one of the most contagious diseases globally. After exposure to the virus, symptoms typically develop within seven to 14 days, manifesting as fever, cough, rash, runny nose, and red, watery eyes. The disease can lead to severe complications, including ear infections, diarrhea, pneumonia, and even brain inflammation.

Measles is one of the most contagious diseases in the world. Symptoms, which appear seven to 14 days after contact with the virus, include fever, cough, rash, runny nose and red, watery eyes. Complications can include ear infections, diarrhea, pneumonia and brain inflammation.

The U.S. has been considered measles-free since 2000, meaning that enough of the country’s population is vaccinated that widespread outbreaks are prevented. The rising number of unvaccinated people in the country could threaten that status. 

The CDC says one dose of the MMR vaccine is 93% effective, while two doses are 97% effective at preventing infection. 

However, vaccination rates have fallen in recent years. During the 2024-25 school year, the CDC reported 92.5% of kindergarteners had received the MMR vaccine, below the 95% coverage public health experts say is needed to prevent outbreaks.

One of 2025’s largest outbreaks started in West Texas and spread into New Mexico, ending in August after hundreds of cases and the deaths of two children and one adult, all of whom were unvaccinated.

In South Carolina, health officials confirmed a measles outbreak in October that has grown to 179 cases, with dozens of new infections reported in recent weeks. Nearly 300 people have been placed in quarantine after being exposed at school.

Another outbreak along the Utah-Arizona border has grown to more than 350 cases combined.

Nationwide, the CDC reports that about 93% of cases this year were among people who were unvaccinated or whose vaccination status was unknown. About 11% of patients have been hospitalized, and more than half are under age 19.

Health officials also warn that genetic links between outbreaks in different states suggest measles could continue spreading into early 2026.

“The trajectory that we’re looking at now is that we do anticipate more cases well into January,” Dr. Linda Bell, South Carolina’s state epidemiologist, told CNN. “What that means for us nationally in terms of how they are defining our designation in this country as having eliminated measles is unclear.”