Pennsylvania crossed 1,000 cases in the measles outbreak in Pittsburgh on Monday, reaching 1,004 reported cases statewide this year. The outbreak, which began in April, has now become one of the largest in the country in decades.
The state added 106 new cases in the past week, bringing the total to 992 cases in the current outbreak and pushing the count above the 1,000-case mark. Pennsylvania has also reported five measles-associated deaths and just under 200 hospitalizations this year.
Chester County and Lancaster County
Chester County reported 84 cases on Monday, while Lancaster County had 391. Across Pennsylvania, the outbreak has spread to more than half of the state’s 67 counties, and about two-thirds of cases have been among adults in Pennsylvania.
That mix leaves local health workers trying to reach exposed people one by one. Dale Weiser, clinical services supervisor for Chester County’s health department, said, "People don’t answer the phone. People hang up. People are absolutely not going to stay home for 21 days."
Adults in Pennsylvania
The case pattern in Pennsylvania differs from the national picture. The CDC recorded 2,289 measles cases across the country in 2025, and adults 20 years and older accounted for a little under a third of U.S. measles cases. In Pennsylvania, adults make up about two-thirds of cases, and about 20% of patients have needed hospitalization.
Rémy Pasco, a research associate at the University of Colorado, has compared the state’s numbers with other large outbreaks. South Carolina had an outbreak that sickened 997 people this year and last, Texas logged 990 measles cases in 2025, and Philadelphia recorded some 1,400 cases in the 1990-1991 outbreak.
Pennsylvania Department of Health
State health officials believe Pennsylvania’s tally is an undercount because more cases may be going unreported. For people in Chester County and Lancaster County, that means the reported total may be only part of the exposure picture, and the harder task now is finding every contact before the virus spreads further.
