Measles cases surge to four times annual US average within weeks

The US has recorded at least 733 confirmed measles cases so far this year, four times the number typically seen in an entire year, the Centers for Disease Control and Prevention said Friday.

The total was reached within just a few weeks, the CDC said, marking a sharp rise from the long-term annual average of about 180 cases since measles was declared eliminated in the country in 2000. The figure excludes last year's record-breaking total of 2,276 cases.

The surge comes as South Carolina experiences what officials describe as its largest measles outbreak in recent memory, while multiple other states continue to report active outbreaks.

States with confirmed cases include Arizona, California, Florida, Georgia, Idaho, Kentucky, Minnesota, Nebraska, North Carolina, North Dakota, Ohio, Oklahoma, Oregon, Pennsylvania, South Dakota, Utah, Virginia, Washington, and Wisconsin, according to the CDC.

Health officials say most outbreaks are concentrated in communities with low vaccination coverage.

"Because it's such an infectious virus, whenever you see measles outbreaks, it in effect highlights areas of the country or communities in which vaccination rates are low," NBC News quoted Demetre Daskalakis, former head of the CDC branch that tracks diseases including measles, as saying.

CDC data show the share of kindergartners vaccinated with the measles, mumps and rubella vaccine has declined from 95% in 2019 to below 93% in 2025.

Public health experts say herd immunity typically requires vaccination rates of about 95% to slow the spread of the virus.

"I think that this highlights that our defenses are down," Daskalakis said, adding that declining vaccination rates have left about 300,000 kindergarteners unprotected.

The CDC says the two-dose MMR vaccine is about 97% effective at preventing measles infection.