Pennsylvania’s measles outbreak has topped 900 cases and killed four people

Pennsylvania’s measles outbreak passed 900 cases on September 28, when the state Department of Health reported 903 confirmed infections in 2026, and four people with measles have died. The Philadelphia Inquirer describes it as the state’s largest outbreak in 30 years. The total is still climbing: 13 new cases were added between Friday and Monday.

The outbreak has reached 39 of Pennsylvania’s 67 counties, and at least 176 people have been hospitalized. Two of the four who died were infants too young to have received the measles vaccine, and the other two were an 18-year-old and a 40-year-old, all of them unvaccinated. The Department of Health publishes the running totals on its measles page, and the September 28 update was the first to carry the outbreak past the 900 mark, up from 890 cases reported in the previous update.

903 cases in 39 counties, and where they cluster

Lancaster County holds the largest share, with 363 cases, according to the Department of Health figures relayed by ABC News. Mifflin County follows with about 105 cases, and the Philadelphia Inquirer reported Chester County as the third largest at 83 cases, tripled since early August. The Inquirer also reported 114 new cases in the past week and described the outbreak as the nation’s largest at present.

At least 11 counties show spread without a known travel history or an identifiable source, ABC reported, which means public-health investigators cannot trace those infections back to an earlier case. Most patients are adults: the majority of cases fall between ages 25 and 49, followed by ages 18 to 24. Fewer than 1 percent of cases, four in all, occurred in people who had been fully vaccinated with MMR, according to the state numbers as reported by WFMZ.

The four deaths, from infants to a 40-year-old

The Inquirer identified the four deaths as two infants from Amish families in Lancaster County, an 18-year-old in Mifflin County who died of neurological complications, and a 40-year-old woman in Jefferson County who had severe respiratory conditions. All four were unvaccinated. The first two measles-associated deaths were confirmed in August, and the state’s measles page calls them the first in Pennsylvania in 35 years.

Hospitalization is more common than the deaths suggest. At least 176 patients have been hospitalized, so roughly one in five confirmed cases (176 of 903) has needed inpatient care.

What exposure looks like and how to respond

Measles symptoms appear 7 to 21 days after exposure and begin with fever, cough, a runny nose and red eyes before a rash spreads, per the Department of Health as summarized by WFMZ. The virus can stay infectious in the air and on surfaces for up to two hours, which is why ABC quoted Dr. Alok Patel advising exposed people to “talk to a healthcare professional” first, rather than walking into an urgent care or emergency room where vulnerable patients wait. The state runs a toll-free hotline at 877-724-3258, and its measles page lists MMR vaccine availability at pediatric offices, pharmacies, county health departments and 59 state health centers, with free shots for children 18 and under who are on Medicaid or uninsured.

Vaccination numbers behind the outbreak

On the prevention side, Pennsylvania has given more than 7,900 MMR doses statewide in 2026, and the Department of Health has run 173 pop-up clinics in affected communities that delivered more than 5,300 doses since the outbreak began in late April, WFMZ reported. Provider demand spiked as cases rose: August saw 49,000 MMR doses administered, nearly double the typical monthly rate of about 25,000. The department’s message has been consistent across updates, with the WFMZ report quoting it as saying the vaccine, given over two doses, “boosts a person’s immune system and provides 97% lifetime protection.”

Chester County’s kindergarten measles vaccination rate is 94.5 percent, just under the 95 percent level generally cited as necessary for herd immunity, per the Inquirer. Chester’s health department has administered 538 MMR vaccines since the outbreak began in April. Health Director Jeanne Franklin told the Inquirer the department is “working all the time with organizations, businesses, community leaders” to raise coverage.

The national picture gives the state numbers context. The CDC’s measles page lists 3,659 confirmed U.S. cases in 2026 as of September 24, and puts national kindergarten MMR coverage at 92.4 percent for the 2025-2026 school year, against the 95 percent threshold. Pennsylvania’s 903 cases therefore account for about a quarter of all cases nationwide, though the two counts were reported on different dates. Whether the weekly tally of about 114 new Pennsylvania cases starts to fall as August’s vaccination surge takes effect will show up in the next Department of Health update.

This article was produced with the assistance of AI and reviewed by Morning Overview editors prior to publication.

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