Chester County reports 83 measles cases as outbreak spreads

Chester County confirmed 83 measles cases by late August, surpassing the total reported by most U.S. states this year and placing the county at the center of Pennsylvania's biggest outbreak in over 30 years. The surge followed an initial spillover from neighboring Lancaster County in late June and accelerated throughout July.

County health officials have stepped up education, organized pop-up vaccination clinics, and begun delivering MMR doses to homes and farms in an effort to contain the virus, especially in under-vaccinated pockets along the western border.

"Public health is now in a race with the disease," said Dale Weiser, clinical services supervisor for the Chester County health department. "It’s going to either burn through all the susceptible people, or we’re going to make fewer people susceptible through vaccination. That’s the only way it ends."

Vaccination coverage among kindergarten students in Chester County sits just below the 95 % threshold considered necessary for herd immunity, and several elementary schools in the eastern part of the county have rates below that level. Health director Jeanne Franklin warned that the virus could spread rapidly through any unvaccinated cluster.

"If it finds that pocket of unvaccinated individuals, it’s going to pop-corn until it finds no one left," Franklin said.

The department has administered more than 500 MMR shots since April and continues to work with hospitals and schools to screen for symptoms and enforce a 21-day exclusion for unvaccinated individuals who are exposed.

Residents expressed mixed concern. Some vaccinated families said they were mainly worried about potential disruptions to school and social activities, while others, such as Sandi Wrigley of Cochranville, described their level of concern as comparable to any common illness.

The outbreak has also affected the Amish community, where two infants died in August and a 20-year-old woman succumbed to the disease while undergoing leukemia treatment. Local outreach programs, including a mobile clinic that visits homes, farms and churches, aim to build trust and provide vaccines in these communities.

"The most important thing is it is community led," said Alisa Jones, CEO of Union Community Care. "We are invited to these homes and farms. We do not invite ourselves."

Statewide, nearly 1,000 measles cases and five deaths have been reported, and officials acknowledge that the actual numbers may be higher due to under-reporting.