Pennsylvania measles outbreak tops 900 cases as 13 new infections confirmed

The Pennsylvania Department of Health said on Monday that 13 new measles cases were confirmed since Friday, bringing the state’s total for 2026 to 903. Cases have been identified in 39 of the state’s 67 counties, and 176 patients have been hospitalized. Four deaths have been linked to the outbreak, two among unvaccinated adults aged 18 and 40, and two among infants too young for the measles, mumps, rubella (MMR) vaccine.

Fewer than one percent of the reported cases involve individuals who are fully vaccinated, according to the department. The majority of infections are among adults aged 25 to 49, followed by those aged 18 to 24. Lancaster County has the highest count with 363 cases, while Mifflin County reports 105.

At least 11 counties show evidence of community transmission, meaning the virus is spreading locally without a known travel source. State health officials have administered more than 8,300 MMR vaccine doses this year, with the highest uptake in August (about 3,500 doses) and September (about 2,500 doses).

Nationally, the Centers for Disease Control and Prevention (CDC) reports over 3,600 measles cases across 45 states and the District of Columbia. The agency has recorded one death this year, though the location was not disclosed. The CDC continues to recommend two doses of the MMR vaccine—first at 12 to 15 months of age and second between 4 and 6 years—citing 93% effectiveness after one dose and 97% after two.

"If you've been exposed, it is important to talk to a healthcare professional, but don't go into an urgent care or an ER because you may be inevitably spreading it to other vulnerable people," said Dr. Alok Patel, a medical contributor for ABC News.

"People who have been exposed may be instructed to quarantine or keep a close eye on their symptoms for up to 21 days, as that is the incubation period for measles," Patel added.