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US Measles Cases Pass 4,400 as CDC Aids Pennsylvania
In brief
The US Centers for Disease Control and Prevention (CDC) has confirmed 4,410 measles cases in the United States so far in 2026, according to its latest update reported on Friday. The agency also said it would send a team of “disease detectives” to Pennsylvania, the state with the largest outbreak, after state officials asked for federal help.
The latest numbers
According to ABC News, the 4,410 confirmed cases were reported by 45 states and Washington, D.C., and 18 of them were among international visitors. Pennsylvania alone has reported more than 1,200 cases, the Philadelphia Inquirer and ABC News said, with ABC reporting six measles-related deaths in the state.
The CDC says about 96% of this year’s cases are in people who were unvaccinated or whose vaccination status is unknown. About 2% had one dose of the measles, mumps and rubella (MMR) vaccine and about 2% had both recommended doses.
What an Epi-Aid is
An Epi-Aid is a short, rapid field investigation in which CDC experts help a state respond to an urgent public health problem, for example by adding staff and tracing how the disease is spreading. A CDC spokesperson told ABC News that Pennsylvania had formally requested the help.
Vaccination advice
The CDC recommends two doses of MMR vaccine, the first at 12 to 15 months of age and the second at 4 to 6 years. It says one dose is about 93% effective against measles and two doses about 97%. ABC News reported that 92.4% of US kindergartners received the vaccine in the 2025-26 school year, down from 95.2% in 2019-20.
To check how many months old a child is before a vaccine appointment, try our age calculator, and see our guide to working out percentages to read case shares. This is general information, not medical advice: talk to a doctor or your local health department about vaccines. ViralScopeHub is not affiliated with the CDC.
Why it matters
Measles spreads very easily, and the US is seeing its largest case counts in decades, so knowing vaccination status matters for families, schools and travellers.
Related free tools: Age Calculator
Sources
- ABC News: More than 4,400 measles cases reported in US as CDC plans to send 'disease detective' to Pennsylvania
- The Philadelphia Inquirer: CDC sends a ‘disease detective’ to Pennsylvania as measles cases top 1,200
- CDC: Measles Cases and Outbreaks
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