More than 1,000 measles cases have been confirmed in the US state of Pennsylvania this year, with five deaths and 198 hospitalisations, making it the largest state outbreak in more than three decades, according to state health officials.
The Pennsylvania Department of Health said on Monday that 1,004 cases had been confirmed across 39 counties, with 27 new cases reported since October 2. The outbreak began in late April.
Only four of the confirmed cases were among people who had received the measles, mumps and rubella (MMR) vaccine, accounting for less than 1% of the total.
Health care providers have also seen a surge in MMR vaccinations. In a typical month they administer about 25,000 doses in Pennsylvania, but more than 49,000 doses were given in August and more than 53,000 in September, the department said.
It said full vaccination offered the best protection against measles, with two doses of the MMR vaccine providing 97% lifetime protection.
In response to the growing outbreak, New York State Governor Kathy Hochul on Monday declared a state disaster emergency. As of October 3, New York had reported 108 measles cases this year, including 92 reported since July 15 in 18 rural counties with under-immunised communities, according to the state government.
The state government said measles cases reported this year had risen markedly beyond the typical number, particularly since July 15, and constituted a significant public health concern.
As of October 1, the United States had reported 3,887 confirmed measles cases in 2026, according to the US Centers for Disease Control and Prevention, making this the worst year for measles in the country since 1991.
