Pennsylvania’s measles outbreak has reached about 890 cases across 39 counties, after 55 new infections were reported on September 28, 2026.

The state’s growing outbreak is part of a wider resurgence of the disease in the United States. Nationwide cases have reached around 3,659 this year, according to Medical Daily, one of the largest totals in decades.

Health officials say low vaccination coverage is driving the spread. Measles is one of the most contagious diseases known, and doctors stress that two doses of the MMR vaccine are highly effective at preventing infection.

The surge has put the country’s measles elimination status under review. The United States had declared measles eliminated in 2000, but sustained outbreaks could threaten that designation. Authorities are urging parents to check their children’s vaccination records and catch up on missed doses.

Measles spreads through the air when an infected person coughs or sneezes, and the virus can linger in a room for up to two hours. Symptoms usually appear a week or two after exposure and include high fever, cough, runny nose, red eyes and a rash. Severe cases can cause pneumonia, brain swelling and death, especially in young children who are not vaccinated.