U.S. measles cases reach 4,410 as Pennsylvania outbreak expands

The Big Picture

The United States has recorded 4,410 measles cases in 2026, according to the Centers for Disease Control and Prevention's latest national update, as a major outbreak in Pennsylvania continues to grow and spread across the state.

The CDC total, reported as of Oct. 15, rose by 330 cases in a week. Pennsylvania reported 1,286 cases as of Oct. 19, with infections now reported in 42 counties. The state sought federal assistance, and the CDC is sending an Epidemic Intelligence Service investigator, commonly described as a disease detective, to support its response.

The national case count is already far above the 2,289 infections reported in 2025, according to The Hill. CDC figures cited by Al Jazeera show 451 measles-related hospitalizations nationwide this year.

What Happened

Pennsylvania had reported 1,222 cases as of Oct. 15, including 86 new infections since Oct. 9. The later state total of 1,286 reflects continued growth over subsequent days.

The CDC said its investigator would work with Pennsylvania health officials after the state requested an Epi-Aid, the agency's term for federal outbreak-response assistance. A CDC spokesperson told NBC News that the agency would continue providing expertise and support to protect public health.

Pennsylvania has administered more than 5,900 doses of the measles, mumps and rubella vaccine through 202 pop-up clinics since the outbreak began in late April, according to Al Jazeera.

Elsewhere, New York Gov. Kathy Hochul declared a statewide measles disaster emergency on Oct. 5, effective through Nov. 4. The order expanded the group of health professionals authorized to administer vaccines and gave nurses greater flexibility to order measles testing, Al Jazeera reported.

Why It Matters

Pennsylvania's health department this week alerted clinicians to increased measles infections among pregnant women and cases of congenital measles, a condition in newborns that is rarely reported in the United States.

The department said 66 pregnant women had been diagnosed with measles since the outbreak began in April. Measles infection during pregnancy raises the risk of miscarriage, early labor and low birth weight, the department told NBC News.

The number of pregnancy outcomes is unclear. Pennsylvania said state law prevents it from releasing details, and NBC News reported that there is no national database tracking congenital measles. Doctors cited by NBC News said at least six babies had been born in Pennsylvania with congenital measles, including at least two who developed pneumonia and required intensive care. Those figures were based on doctors' accounts rather than a state case registry.

Congenital measles can cause severe illness and may be associated with later neurological and immune system complications, according to Pennsylvania health officials. The department said vaccination before pregnancy is the best way to prevent the condition. Pregnant people cannot receive the MMR vaccine because it contains a weakened live virus.

Background

CDC data cited by Al Jazeera show that U.S. kindergarten measles vaccination coverage declined from 95.2% in the 2019-2020 school year to 92.4% in 2025-2026. The agency estimated that gaps in coverage left about 280,000 kindergarteners at risk.

Children and teenagers ages 5 to 19 accounted for 42% of U.S. measles cases this year, while adults 20 and older accounted for 41%, according to CDC figures cited by Al Jazeera. Children younger than 5 made up 17% of reported cases.

Lancaster County has been at the center of Pennsylvania's outbreak. The Guardian reported that it is the largest county in the state without its own health department, a factor local officials say complicates communications and rapid local response.

What Happens Next

The CDC on Oct. 20 added a third measles death to its national tracker after the National Center for Health Statistics verified measles as the underlying cause on a death certificate. The agency did not identify the state where the death occurred.

Federal and state death totals differ because the CDC has shifted to mortality data from the National Center for Health Statistics rather than relying on state health department reports. Pennsylvania reported five measles-associated deaths as of Oct. 19, according to Al Jazeera, while The Guardian reported that the state had confirmed six. State and federal totals may change as death records and investigations are reviewed.

Health officials are expected to continue vaccination outreach, case monitoring and support for affected communities as the Pennsylvania outbreak and the national count evolve.