The Largest Measles Outbreak in the United States Since 2000

The measles outbreak in Pennsylvania has become the largest in the United States since the highly contagious virus was declared eliminated in 2000, with the number of infected people surpassing 1,000, the highest since 1991.

According to Pennsylvania health officials, a total of 1,078 cases of measles have been reported in 2026 alone. The outbreak began in April, with 12 cases reported in January and March combined, and the remaining 1,066 cases since then. In the past seven days, 145 new cases have been recorded, with 74 cases identified since the previous update on Monday. It is worth noting that 40 of the 74 newly reported cases occurred more than two weeks ago and are being added to the tally.

Out of the total cases, 207 individuals have been hospitalized and unfortunately, five people have died, including a newborn, a 6-week-old, an 18-year-old, and an infant aged 20 to 40 years old. All fatalities were in unvaccinated individuals, with the two infants being too young to receive the vaccine.

Measles outbreaks have been on the rise due to declining vaccination rates across the country. The outbreak in Texas from January to August 2025 saw 762 cases, while the South Carolina outbreak, the previous record holder, ended in April with 997 cases. Pennsylvania has now surpassed both states with 1,066 outbreak-related cases, and with 34 new infections reported since Monday, the outbreak shows no signs of slowing down.

Measles Emergency and Vaccination Efforts

Measles was declared eliminated in the U.S. in 2000 due to successful vaccination efforts. However, the recent outbreaks suggest a decline in vaccination rates, leading to a resurgence of the virus. Experts from the Pan American Health Organization (PAHO) are set to review data in November to determine if the U.S. has lost its measles-free status. It is widely anticipated that the country has lost this status, following in the footsteps of Canada, which lost its eliminated status in 2025.