Pennsylvania measles outbreak tops 1,000 cases, largest in US since 1991

State reports five deaths; CDC lists two in same outbreak

The Pennsylvania Department of Health on October 7 reported 1,066 confirmed measles cases since the outbreak began in April, surpassing the 997 cases recorded in a South Carolina outbreak that ended earlier in 2026 and becoming the largest US outbreak in 35 years. State health officials said five people have died. The federal Centers for Disease Control and Prevention currently lists two measles deaths in Pennsylvania; the state has asked the CDC for emergency help, but on the condition that the federal agency recognize all five deaths as measles-associated.

Nationally, the US has recorded more than 3,800 measles cases in 2026, with 40 outbreaks reported through October compared with 16 in all of 2024, according to the CDC. For decades before the recent surge, the US recorded as many as a few dozen or hundred measles cases each year. Historic outbreaks in Texas, Utah and South Carolina over the past nearly two years have fueled decades-high case counts. The country is on the verge of losing the measles elimination status it achieved in 2000, after successive years of outbreaks fueled by declining vaccination rates. The last comparable surge in the late 1980s and early 1990s sickened tens of thousands and prompted public-health officials to recommend two doses of the measles, mumps and rubella, or MMR, vaccine, which was introduced in the US in the 1970s. Those vaccination efforts led to elimination in 2000.

“We’re living with measles as an ongoing public health threat to the United States,” said Jennifer Nuzzo, director of the Brown University Pandemic Center. “As long as measles continues to transmit in the country, it will find its way into these exquisitely vulnerable communities and cause massive outbreaks.”

Lancaster County, where about 400 people have been infected and three have died, has been the center of the state’s outbreak. According to the Pennsylvania Department of Health, 87.6% of kindergartners in the county were fully vaccinated against measles in the 2025-26 school year. Members of the Amish community call the county home, riding horse-drawn buggies and operating farms with chickens, pigs, cows and horses on their properties just outside of the city. A 2025 state health department report found that only about a quarter of the county’s large Amish community was vaccinated against measles.

In nearby Chester County, public-health nurses are visiting family homes to vaccinate groups of church friends and setting up vaccine clinics at restaurants and firehouses, according to Jeanne Franklin, director of the Chester County Health Department. “That human interaction—the word-of-mouth,” Franklin said. “That is the key in Pennsylvania’s outbreak right now. It’s not twisting arms.”

Some Pennsylvania doctors are treating measles for the first time. They are seeing more patients with rare but severe outcomes of the disease, including severe pneumonia and encephalitis, a form of brain swelling that can lead to disabilities. Measles patients are being placed in negative-pressure rooms to avoid infecting others in hospitals. “We’re learning on the fly,” said Dr. John Goldman, an infectious disease specialist at the University of Pittsburgh Medical Center in Harrisburg. Public-health leaders expect measles to keep spreading until they reach the herd-immunity threshold of roughly 95% of people either having contracted the virus or been vaccinated.

Goldman said several cases have involved babies contracting the disease in utero or at birth, which is rare. In Pennsylvania, one newborn has died with the disease shortly after birth.

Kate Mercogliano, a 38-year-old lawyer, said a possible exposure reported at the Children’s Hospital of Philadelphia last month prompted her to get her seven-month-old vaccinated about five months before her daughter was due for her first shot. “Once I heard about that, I was like, ‘No, I absolutely have to get my baby the early vaccine,’” Mercogliano said.

Pennsylvania’s classification of an infant’s death as “measles-associated” in August has prompted a political debate over vaccinations at the state and federal level that is ongoing.