Already in 2025, the United States has reported more measles cases than in any full year since the early ‘90s, according to federal data. And that record-setting case count has been driven by a massive outbreak that began in Texas.

Other U.S. states with active outbreaks — which the CDC defines as three or more related cases — include Arizona, Colorado, Georgia, Illinois, Iowa, Kansas, Michigan, Montana, New Mexico, North Dakota, Oklahoma and Utah.