Measles outbreak in Pennsylvania intensifies to at least 835 cases

Health authorities in Pennsylvania said Wednesday that an outbreak of measles has grown to 835 cases across 39 counties in the state.

43 new positive cases have been identified since Monday. Over the course of the outbreak, 164 people have been hospitalized and four people have died.

Pennsylvania has stepped up vaccination for MMR in response.

"Over the first three weeks of September 2026, health care providers across Pennsylvania have administered more than 38,000 MMR vaccine doses – in a typical month, it’s just 25,000," Pennsylvania's Department of Health said in a statement on the outbreak. "Getting vaccinated is the best protection against the measles virus; the vaccine is proven 97 percent effective at preventing measles for life after two doses."

RELATED STORY | Pennsylvania reports first measles deaths in 35 years

Meanwhile, officials are warning of other possible exposure to measles in the St. Louis area in Missouri.

The possible exposure took place between Sept. 12 and Sept. 14 at Busch Stadium and at local restaurants and a grocery store.

Two people may also have been involved in measles exposure when they took a train from Missouri to Chicago on August 27.

The Centers For Disease Control and Prevention says there have been 3,471 confirmed measles cases so far in the U.S. this year.