The United States is currently grappling with its worst measles resurgence in decades, driven by widespread outbreaks across multiple states, according to data from the U.S. Centers for Disease Control and Prevention.
Public health authorities reported 4,588 measles cases across the country as of October 22, 2026, according to Reuters, more than double the total number recorded for the entirety of 2025. The CDC noted that 96% of individuals who contracted the virus in 2026 were either unvaccinated or had an unknown vaccination status.
Pennsylvania Outbreak Centers on Lancaster and Mifflin Counties
Pennsylvania has emerged as the epicenter of the national resurgence, recording at least 1,338 confirmed measles cases across 44 counties as of late October, the Pennsylvania Department of Health reported. More than 250 people have been hospitalized statewide, and five deaths have been confirmed by state health officials. The hardest-hit areas include Lancaster County, where a local Amish community is being impacted the most. Steve Nolt of Elizabethtown College told the Australian Broadcasting Corporation that Amish families are large and frequently gather for church services held inside homes, which has accelerated the spread. Additionally, the Pennsylvania Department of Health issued a health advisory warning clinicians to monitor infants born to mothers infected with measles during pregnancy, noting that 66 pregnant women have contracted the virus during the outbreak, according to Medical Daily.
National Resurgence Spans Multiple States
Beyond Pennsylvania, several other states are managing substantial outbreaks. In South Carolina, there have been at least 997 measles cases in 2026, according to the South Carolina Department of Public Health. Utah health officials reported more than 700 diagnoses this year, though no new cases have been identified in the state for three weeks. In New York, Governor Kathy Hochul declared a disaster emergency earlier in October following over 160 confirmed cases.
National health data indicates that children and teenagers aged 5 to 19 represent the largest group of infections at 42%, closely followed by adults aged 20 and older at 41%, Reuters reported.
Vaccine Efficacy and Public Response
Health officials emphasize that immunization remains the most effective defense against the virus. The measles vaccine is 97% effective at preventing the disease, according to the CDC.
Driven by rising awareness of the outbreak, Pennsylvania residents have accelerated vaccination efforts. State health providers administered more than 39,000 measles vaccines during the first three weeks of October, surpassing the typical monthly average of 25,000 doses, according to state health data.
Frequently Asked Questions About the Resurgence
How effective is the MMR vaccine against the current strain?
The measles vaccine is 97% effective at preventing the disease, according to data from the CDC.
Which age groups are most affected by the 2026 outbreak?
Children and teenagers aged 5 to 19 account for 42% of all reported cases, while adults aged 20 and older make up 41% of infections, according to CDC figures released in October 2026.
How many counties in Pennsylvania have reported measles cases?
The Pennsylvania Department of Health confirmed that measles has spread across 44 counties in the state, with Lancaster and Mifflin counties experiencing the highest concentrations of the disease.
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