Pennsylvania health officials reported Monday that 1,004 measles cases have been confirmed this year, with 198 hospitalizations and five measles-associated deaths, making it the largest state outbreak in more than three decades, according to The Guardian and NBC News. The state Department of Health says the outbreak began in April west of Philadelphia and has now reached 39 of Pennsylvania's 67 counties, per the Philadelphia Inquirer. Lancaster County, home to one of the nation's largest Amish and Mennonite communities, is the epicenter with 391 cases. Fewer than 1% of the state's cases are among people fully vaccinated with the MMR vaccine, according to Pennsylvania health officials cited by ABC7.

Doctors are describing severe complications in the Pennsylvania outbreak. According to NBC News, Dr. Evan Shirey of Penn State Health said children are presenting with dehydration, liver inflammation, and in some cases severe, irreversible neurological damage from brain inflammation. NBC also reports the five deaths include a teenager with severe brain inflammation, a 40-year-old woman with asthma, two infants too young to be vaccinated, and an unvaccinated Lancaster County resident.

The outbreak's death toll has become entangled in a dispute between Pennsylvania Governor Josh Shapiro and US Health Secretary Robert F. Kennedy Jr. The Guardian reports the state's fatalities are not included in the CDC count because of a disagreement over how measles-related mortality is classified, with Kennedy publicly questioning whether the recorded deaths were directly caused by measles and Shapiro calling him "incompetent." The AP via the Marietta Daily Journal reports the CDC only began acknowledging measles-associated deaths in Pennsylvania two weeks ago, adding its second tally last week. Meanwhile, Gothamist reports New York joined 15 states suing the Trump administration over its changed childhood vaccine schedule.

Experts expect the outbreak to persist. "I would bet that this goes on for at least another three to six months," Dr. John Goldman, an infectious disease expert at UPMC, told NBC News, noting vaccination increases have not been enough to stop transmission. Pennsylvania health department staff have administered just over 8,800 MMR doses in response, per ABC7. Ohio is also seeing a growing outbreak with more than 200 cases, and The Guardian reports international health officials will meet in November to determine whether the US and Mexico have lost their measles-free status. New York's emergency order runs through Nov. 4.