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

Sixty-six pregnant women in Pennsylvania have been diagnosed with measles since the state's outbreak began in April, and doctors are now reporting babies born with congenital measles.

The United States has recorded 4,410 measles cases this year, according to the CDC's October 15 update, a jump of 330 in one week. Pennsylvania reported 1,286 cases as of October 19, with infections now reported in 42 counties. The state asked for federal assistance, and the CDC is sending an Epidemic Intelligence Service investigator, often called a disease detective.

Why it matters: Measles during pregnancy raises the risk of miscarriage, early labor and low birth weight. Pennsylvania's health department warned clinicians this week about more infections in pregnant women and congenital measles, in which a baby is infected around birth. There is no national database tracking those cases, and the state cannot release individual pregnancy outcomes.

NBC News reported that doctors have anecdotally identified at least six Pennsylvania babies born with congenital measles. At least two developed pneumonia and needed intensive care, according to those doctors. Congenital measles can also bring neurological and immune-system complications that require long-term monitoring.

The count problem: Pennsylvania reported five measles-associated deaths as of Monday. The Guardian previously reported six confirmed deaths in the state, while Al Jazeera said a sixth was under investigation. The CDC's national tracker lists three deaths after the National Center for Health Statistics verified measles as the underlying cause on a death certificate. That lower federal figure reflects a different system, using national mortality records rather than state health department reports.

The number underneath it: U.S. kindergarten measles vaccination coverage fell to 92.4% in the 2025-2026 school year, from 95.2% in 2019-2020, according to CDC data cited by Al Jazeera. The agency estimates roughly 280,000 kindergarteners are exposed to coverage gaps. Pennsylvania has administered more than 5,900 MMR vaccine doses through 202 pop-up clinics since the outbreak began, but the outbreak has already reached far beyond Lancaster County, its initial epicenter.

The next CDC update will show whether the national case count is still climbing at the same weekly pace.