Pennsylvania Measles Outbreak Tops 1,000 Cases, Becoming the Largest in the US Since Elimination in 2000

HARRISBURG, Pa. — Pennsylvania's measles outbreak has surpassed 1,000 cases, becoming the largest in the United States since the highly contagious virus was declared eliminated in 2000 and the biggest single outbreak in the country since 1991.

The Pennsylvania Department of Health reported Wednesday that 1,078 measles cases have been confirmed across 41 counties so far in 2026. Of those, 1,066 are linked to the current outbreak, which began in late April. The remaining 12 cases were recorded in January and March.

The state added 145 cases over the past week, including 74 reported since its previous update on Monday. Health officials said more than 40 of the newly added cases involved people who were sick more than two weeks ago and are no longer contagious, but whose infections were only recently reported and confirmed.

So far, 207 people have been hospitalized and five have died.

"We are having a measles outbreak in Pennsylvania, and we are encouraging people who are not vaccinated to please get vaccinated," Pennsylvania Health Secretary Dr. Debra Bogen told WFMZ-TV.

Five deaths, all unvaccinated

All five deaths occurred during the current outbreak, and all were in people who were not vaccinated against measles.

The victims include a newborn, a 6-week-old baby, an 18-year-old, a 20-year-old and a 40-year-old woman. The two infants were too young to receive the measles, mumps and rubella vaccine, which is typically given in two doses starting at 12 months of age.

The most recent death, of a 20-year-old in Lancaster County, was confirmed earlier this month.

The deaths make the Pennsylvania outbreak not only the largest but also the deadliest in the United States in more than three decades.

Some of the deaths drew controversy after federal health officials led by Health and Human Services Secretary Robert F. Kennedy Jr. questioned whether measles had caused them, before coroners confirmed the virus was responsible. The Centers for Disease Control and Prevention has said it is working with state epidemiologists on a standard definition for measles-related deaths, according to Reuters.

Measles kills one to three of every 1,000 people infected, according to the state health department.

Lancaster County hardest hit

Lancaster County remains the epicenter of the outbreak, with 401 reported infections as of Wednesday, Reuters reported.

Children and teenagers under 18 accounted for about a third of all cases. Fewer than 1% of patients were fully vaccinated, with just four cases reported among vaccinated people, according to state data.

Bogen said the outbreak has been difficult to contain partly because measles initially resembles other common illnesses.

"The problem is that early signs of measles look very similar to common respiratory viruses," she said, describing symptoms that begin with fever, cough and runny nose before the characteristic rash appears.

Measles is one of the most contagious diseases known. The virus spreads through the air and can linger in a room for up to two hours after an infected person leaves. Up to 90% of unvaccinated people exposed to the virus will become infected.

Complications can include pneumonia, brain swelling and death. Young children and pregnant women face the highest risk.

Surpassing South Carolina and Texas

Pennsylvania's outbreak has now overtaken two other large outbreaks from the past two years.

An outbreak in South Carolina, which ended in April with 997 cases, had held the record for the largest outbreak since elimination. An outbreak centered in West Texas from January to August 2025 infected 762 people and killed two unvaccinated children.

The last U.S. outbreak larger than Pennsylvania's occurred in New York in 1990 and 1991, when more than 4,500 people were infected during a nationwide resurgence.

With dozens of new cases still being reported each week, Pennsylvania's outbreak shows no sign of ending soon.

National cases at 35-year high

The Pennsylvania outbreak is driving a sharp rise in measles nationwide.

As of Oct. 1, the CDC had reported 3,887 measles cases in the United States this year, the highest annual total since 1991, when the country recorded 9,643 cases. The 2026 total is already nearly double the 2,012 cases reported in all of 2025.

Health officials are preparing to review the country's measles elimination status following dozens of new outbreaks this year. The U.S. would lose that status if a single chain of transmission continues for 12 months or more.

Measles was declared eliminated in the United States in 2000, meaning the disease was no longer continuously spreading in the country, thanks to widespread vaccination.

Public health experts have blamed the resurgence on falling vaccination rates, fueled by vaccine hesitancy and misinformation. Kindergarten vaccination rates nationwide have dropped below the 95% threshold needed to prevent outbreaks.

Vaccination surge

Pennsylvania officials said the outbreak has spurred a sharp increase in vaccinations.

"We didn't have cases for decades because of the effectiveness of the vaccine, and we're seeing an increase, unfortunately, because we have people who are not protected," Bogen said.

She said more than 53,000 MMR vaccines were administered across Pennsylvania in September, which officials said was more than double the usual monthly total.

State health center staff have administered more than 5,700 MMR vaccinations at 198 pop-up clinics in affected communities since the outbreak began, according to the health department.

Two documented doses of the MMR vaccine provide about 97% protection against measles for life, health officials said.

Local health departments, including in Allentown, are holding free vaccination clinics throughout October.

What to watch for

Health officials urge anyone who develops a high fever, cough, runny nose, red or watery eyes and a rash to call a doctor or emergency room before arriving, so staff can take precautions to avoid exposing others.

Symptoms typically appear seven to 14 days after exposure. People with measles can spread the virus from four days before to four days after the rash appears.

The state health department said it will continue to update case counts, hospitalizations and deaths on its online measles dashboard.