An unvaccinated Lancaster County resident became Pennsylvania's fifth measles death as the statewide outbreak reached a record 943 confirmed cases, the Pennsylvania Department of Health announced Wednesday, Sept. 30.

The state did not release the person's age or other identifying details. Lancaster County, where about 40% of the state's cases have been concentrated, has been the outbreak's epicenter since it began in late April, according to CNN.

Bucks County had no confirmed cases as of Sept. 18, the most recent county-specific update available. Bucks County Health Department spokesman Neil Ruhland said in a Sept. 19 statement to the Bucks County Courier Times that the county could see a case in the near future because viruses do not stop at county borders.

Statewide toll grows

The 943 cases span 39 counties, with 40 new infections reported since Monday, Sept. 28. A total of 176 people have been hospitalized, roughly one in five of those infected. Nearly all cases involve unvaccinated people; only four of the 943 infections occurred in vaccinated individuals, the health department said.

The last year the United States recorded more than four measles deaths in a single year was 1991, CNN reported.

The four earlier Pennsylvania deaths include two infants in Lancaster County, an 18-year-old from Mifflin County and a 40-year-old woman from Jefferson County, according to WHYY.

Bucks County vaccination rates

Bucks County's kindergarten measles, mumps and rubella (MMR) vaccination rate stood at 93.7% as of September, according to Ruhland. Medical experts classify 95% as the threshold for herd immunity, the level needed to stop community transmission.

The county's overall student MMR rate averaged 95.6%, down from 97.6% during the 2019-2020 school year, according to state data reported by Central Bucks Now. At least 12 Bucks County schools recorded kindergarten MMR rates below 90% in 2024, most of them faith-based private or charter schools, according to a Philadelphia Inquirer analysis reported by Central Bucks Now.

Experts expect cases to rise in winter

Dr. Paul Offit, director of the Vaccine Education Center at Children's Hospital of Philadelphia, told TribLive that measles infections typically peak in winter and early spring.

"I think it's going to get worse. I think it's going to get much worse," Offit said.

Statewide, health workers have administered more than 5,500 MMR vaccinations at 180 pop-up clinics in affected communities since the outbreak began. More than 53,000 doses were given across Pennsylvania in September, more than double the typical monthly volume, the health department said.

The Bucks County Health Department recommends residents confirm their child's vaccine is up to date and keep vaccination records available. Residents who believe they were exposed to measles can call the state health hotline at 877-724-3258.