The Ongoing Measles Outbreak Has Reached a New Peak

America’s terrible year of measles is far from over. Several states have reported more cases of the vaccine-preventable viral disease as of late, while the country as a whole has hit a new record high.

Health officials in Michigan, California, and Illinois confirmed new cases of measles this week. According to the Centers for Disease Control and Prevention, 2025 has seen the highest number of cases since the disease was locally eliminated from the country a quarter century ago. Though the largest outbreaks this year have since ended, there remains a real chance measles could once again reestablish itself in the U.S.

New threats

Officials in Orange County, California^[1], and Cook County, Illinois,^[2] reported a single new case of measles each this week.

The California case involved a toddler who had recently traveled domestically, and officials have notified people who could have been exposed to the child at a health care setting. No other community exposure is suspected, however, since the family had been isolated during the most likely period for transmission.

The Illinois case involved an adult who likely caught measles from an infected individual that health officials had identified several weeks earlier. It’s the third case reported in the county this year.

The largest new threat of measles comes from Minnesota, however. The Minnesota Department of Health reported^[3] 10 new cases this week, bringing the state’s total tally to 17 this year. Seven of the cases are connected to three earlier cases, while the remaining three are unrelated and tied to international travel, presumably from areas where measles remains endemic. As is often true, all of the new Minnesota cases have occurred among people unvaccinated against measles.

Meanwhile, as of September 30, there have been a total of 1,544 confirmed cases of measles in the U.S. so far this year, the CDC reported^[4] this week. 92% of these infections have involved people who are unvaccinated or have an unknown vaccination status. The tally in 2025 is well above the previous modern high—1,274 cases in 2019—and is the most since 1992, which saw over 2,000 cases.

Good and bad news

On the positive side of things, New Mexico officially declared^[5] the end of its large-scale outbreak late last week. The state had documented 100 cases of measles dating back to February 2025, the second largest outbreak of any state this year. The largest outbreak occurred in Texas, which saw 762 cases; the state declared^[6] its outbreak over in mid-August.

These outbreaks didn’t end without causing their fair share of misery, however. Around 200 children have been hospitalized for measles this year in the U.S., for instance, while three have died from it—the first U.S. deaths reported in a decade.

Measles can have long-term health consequences as well. Studies have shown, for instance, that measles can induce^[7] a form of “immune amnesia,” causing people’s immune systems to lose their memory of other past infections.

These latest cases also demonstrate that measles can easily spark new clusters of illness at a moment’s notice, particularly in regions where vaccine uptake is relatively low. Only a handful of states in the U.S. currently have^[8] childhood vaccination rates for measles above 95%, the level at which herd immunity can reliably prevent widespread outbreaks. And even highly vaccinated states have communities where coverage is much lower than average (Texas’s overall vaccination rate in 2023 and 2024 was just a smidge below 95%, for instance).

Unfortunately, while a majority of Americans do still support^[9] vaccines and current vaccine requirements, many of the country’s leaders don’t seem to.  Robert F. Kennedy Jr. has downplayed^[10] the country’s measles outbreaks and regularly undermined^[11] vaccines since taking over as the U.S. Health and Human Services Secretary this year, as has President Donald Trump.

Just last week, both men took the podium to once again endorse^[12] the debunked link between vaccines and autism. Trump also reiterated his support to separate the perfectly safe and effective combination measles, mumps, and rubella (MMR) vaccine—a change that would undoubtedly lower vaccination rates for all three diseases.