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Pennsylvania’s measles outbreak is spreading unusually among adults
Adults account for roughly two-thirds of Pennsylvania’s measles cases, a reversal of the illness’s usual age pattern. The state has the nation’s worst outbreak.
Adults make up about two-thirds of measles cases in Pennsylvania, an unusual pattern for an illness commonly associated with children. The state is experiencing the worst measles outbreak in the country, according to information published Oct. 22, 2026.
The adult share is nearly the inverse of how measles has typically spread, putting the focus on infections beyond childhood. The available figures do not specify the total number of cases or explain why adults account for such a large proportion.
The Pennsylvania Department of Health has held a measles, mumps and rubella vaccine clinic at the Robert Fulton Fire Company in Peach Bottom, Lancaster County. The clinic underscores the role of vaccination in the state’s public-health response as the outbreak continues.