Measles Outbreaks in the United States Hit Highest Point in Decades
The United States is seeing the highest number of new cases of measles since the highly contagious disease was declared eradicated 25 years ago.
There is an ongoing outbreak along the border between Arizona and Utah, with more than 100 confirmed cases. Nearly 60 of the cases were in Arizona, mostly in the area of Colorado City in Mohave County, CNN reported. Reported cases of measles have climbed to 57 in Utah, with 43 of the diagnosed cases in southwestern counties of Beaver, Garfield, Iron, Kane, and Washington, according to the state.
Potential exposures to measles may have occurred between 2 and 7 August in both states, according to officials in Mohave County. The current outbreak is already the second-largest in the country this year. An outbreak is defined as an incident where three or more related cases occur.
“The number of measles cases hit a 34-year high this summer, largely driven by the so-called ‘Southwest outbreak,’ which grew to more than 880 cases across Texas, New Mexico and Oklahoma,” The New York Times reported. “Several epidemiologists agreed that the current scale and spread of cases most closely resembles the large outbreaks of the early 1990s—before nationwide immunization campaigns and school vaccine mandates helped the United States declare the virus eliminated.”
Since the COVID-19 pandemic, there has been an increase in parents not vaccinating their children. The Southwest Utah Public Health Department reported that all but one of the 27 confirmed cases involved an unvaccinated school-age child, according to NBC News. In the region, more than 19 percent of kindergartners were not vaccinated against measles for the 2024-2025 school year. Utah allows parents to exempt their children for medical, religious, or personal beliefs, according to data published by the Utah Department of Health and Human Services (DHHS).
In Mohave County, Arizona, an estimated 90 percent of kindergartners were fully vaccinated against measles for the 2019-2020 school year. That vaccination rate dropped to 78 percent by the 2024-2025 school year.
In an interview with the Times, Jessica Payne, an epidemiologist that leads the immunization program for the Utah DHHS, credited the increase in schoolchildren not receiving routine vaccines or shots to “the politicization of vaccines that developed during the pandemic,” which Payne said contributed to a widespread anti-vaccine sentiment in the area.
Texas. So far, the most recent deadly outbreak of measles in 2025 was in the Lone Star State, with 762 cases confirmed since late January, according to the Texas Department of State Health Services.
“More than two-thirds of the cases were in children. Ninety-nine people were hospitalized over the course of the outbreak, and there were two fatalities in school-aged children,” the department reported. The two children were not vaccinated and had no known underlying conditions.
The outbreak was considered ended in August after 42 consecutive days without a new case—42 days being double the virus’s maximum incubation period (the amount of time between when someone is exposed to the virus and when that person falls sick).
“The end of this outbreak does not mean the threat of measles is over. Since there are ongoing outbreaks of measles in North America and around the world, it is likely that there will be additional cases of measles this year in Texas. Healthcare providers should continue to be vigilant and test for measles if their patient has symptoms compatible with the virus,” the department said.
South Carolina. More than 150 unvaccinated schoolchildren from two schools were quarantined after there was an exposure to measles at the schools—a public elementary school and a public charter school in Spartanburg County.
As of 17 October, there have been 19 reported cases of the disease, with 15 of them occurring in Spartanburg County, according to the state’s Department of Public Health.
“Some cases are travel-related exposures or close contacts of known cases. Other cases have no identified source, suggesting that measles is circulating in the community and could spread further,” the department said.
Previous Outbreaks
Measles was declared eliminated in the United States in 2000, and between 2000 and 2025, the United States only recorded 10 “large” measles outbreaks, which the CDC defines as more than 50 related cases.
While measles cases have occurred since 2000, the number can only increase to the level of an outbreak or a large outbreak if enough people within an affected community are unvaccinated against the virus. To achieve and maintain herd immunity against the virus, at least 95 percent of a population must be immune against it, either due to vaccinations or a previous infection of the disease, according a resource from the Cleveland Clinic. With herd immunity, the measles virus would be difficult to spread to other people and would lower the likelihood of the virus mutating into a new strain.
While there were 16 outbreaks reported in 2024, there have already been 44 reported in 2025.
As of 14 October, the U.S. Centers for Disease Control and Prevention (CDC) had confirmed 1,573 cases of measles among residents in Alabama, Alaska, Arizona, Arkansas, California, Colorado, Florida, Georgia, Hawaii, Idaho, Illinois, Indiana, Iowa, Kansas, Kentucky, Louisiana, Maryland, Michigan, Minnesota, Missouri, Montana, Nebraska, New Jersey, New Mexico, New York, North Dakota, Ohio, Oklahoma, Oregon, Pennsylvania, Rhode Island, South Carolina, South Dakota, Tennessee, Texas, Utah, Vermont, Virginia, Washington, Wisconsin, and Wyoming. Another 23 cases have been reported in international visitors to the United States.
