Pennsylvania Reports Largest U.S. Measles Outbreak Amid Rising National Cases

Pennsylvania is experiencing the largest measles outbreak in the U.S. with 1,078 confirmed cases as of October 7, 2026. This contributes to a national total of 3,887 cases reported by the CDC in 2026, a notable increase from 2,289 cases in the previous year. The outbreak in Pennsylvania is primarily affecting communities characterized by lower historical vaccination rates, underscoring the importance of immunization in preventing disease spread.