Measles Update: May 26

May 27, 2025

As of May 23rd, a total of 1,046 cases across by 31 jurisdictions have been reported, up from 1,024 on May 16th.
The vast majority of confirmed cases—96%—involve individuals who are either unvaccinated or whose vaccination status is unknown.
Young children under age 5 account for nearly a quarter of all hospitalizations.
So far in 2025, there have been 14 reported outbreaks, with 92% of confirmed cases (961 out of 1,046) linked to these outbreaks. By comparison, 2024 saw 16 outbreaks, with 69% of cases (198 out of 285) outbreak-associated. The CDC defines a measles outbreak as three or more related cases.
- What this means for the public: Even though the number of outbreaks is slightly lower so far this year (remember we still have half a year to go), each outbreak this year is much larger and more intense. This suggests that once measles is introduced into a community especially one with low vaccination rates, it spreads rapidly and widely. For the average person, this means the risk of exposure is higher if you're in or near an outbreak zone, and especially if you're unvaccinated. It’s a strong signal that community immunity is weakening and that localized outbreaks can escalate quickly. Getting vaccinated and ensuring your children are fully vaccinated is the most effective way to protect yourself and prevent further spread.