US measles cases exceed 3,400 as Philadelphia airport issues exposure warning
More than 3,400 measles cases have been reported in the United States this year, prompting health officials to warn travelers who passed through Philadelphia International Airport of possible exposure.
The Philadelphia Department of Public Health announced that a traveler with measles was present in terminals B and F, and connecting areas to terminals C, D and E, between 7:25 p.m. on Sept. 13 and 12:05 a.m. on Sept. 14. The individual did not leave the airport, leading officials to advise anyone who was in those areas during that window to verify their vaccination status, monitor for symptoms and contact a health-care provider if they are not immune, are pregnant, infants, or immunocompromised.
The warning comes as the Centers for Disease Control and Prevention (CDC) recorded 3,471 confirmed measles cases nationwide as of Sept. 17, surpassing the total of 2,289 cases reported for the entire previous year. Pennsylvania leads the outbreak with 745 cases in 2026, up sharply from 16 in 2025, while South Carolina and Utah report 670 and 527 cases respectively.
The CDC notes that 95 % of the confirmed infections are linked to 39 identified outbreaks this year. It also reports that 44 % of cases involve individuals aged 5-19 and 18 % involve children under five. The agency emphasizes that measles spreads through airborne droplets and can remain infectious in the air for up to two hours.
"This week's measles exposures are a reminder of how important it is for all of us to be up to date on our vaccinations," said Philadelphia Health Commissioner Dr. Palak Raval-Nelson.
Vaccination remains the primary preventive measure. One dose of the measles-mumps-rubella (MMR) vaccine is about 93 % effective, and two doses raise effectiveness to roughly 97 %. The CDC also reports a decline in MMR coverage among kindergarteners to 92.4 % for the 2025-2026 school year, with exemptions rising to 4.2 %.
People who may have been exposed and develop symptoms through Oct. 5 are urged to contact their doctor promptly and mention the possible exposure before seeking care.