TRACKING EMERGING VIRUSES – October 23, 2025 – Measles
“Just as one large measles outbreak peters out in the United States, another outbreak of the virus has taken off along the border of Utah and Arizona.
The new outbreak began in August and has sickened more than 100 people, making it the second-largest cluster of cases in the country this year. A majority of the cases are in unvaccinated people.
It comes during an already bleak year for the nation’s public health: 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. 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.”
“There are several parallels between the current situation at the Utah-Arizona border and the outbreak that exploded from the Western edge of Texas in January: Both started in rural towns with a sizable population of children who had not been immunized against measles, mumps and rubella. And in both outbreaks, the virus traveled to a neighboring state and took root in similarly vulnerable pockets.” (1)
“The nation’s second-largest measles outbreak this year is spreading beyond its epicenter along the Utah-Arizona border.
Most of the known measles cases — 123 as of Wednesday — are linked to a tight-knit community of twin towns: Colorado City, in Mohave County, Arizona, and Hildale, which is in Washington County, Utah. Within the past few weeks, there have been three cases in nearby, larger towns, such as Hurricane and St. George, Utah. Those exposures occurred in hospital and urgent care settings, according to the Southwest Utah Public Health Department.
There is no discernible border; residents live, work and worship interchangeably between the two towns.
Many of the clusters started in schools, said David Heaton, public information officer for the health department. “But now we have community spread,” he said.”
“All three affected counties have vaccination rates far lower than the 95% experts say is needed for herd immunity.
Given the low vaccination rates, Heaton and his team had been bracing for a measles outbreak to hit the region. “We were preparing for it,” he said. “It was a matter of time before it came here.”” (2)
“Measles cases have surged worldwide to a 25-year high, due to low vaccine coverage and the spread of misinformation about vaccine safety. However, there is added concern in parts of Latin America over unequal access to healthcare and the worrying situation in the US, which is facing its worst measles outbreak in decades following a reversal of vaccine policy led by Donald Trump’s health secretary, Robert F Kennedy Jr.”
“Measles was successfully eliminated from the Americas in 2016, and then again in 2024, but the continent is now at risk of losing its measles-free status. There have been 11,668 cases reported across 10 countries in North and Latin America, according to the latest data from the Pan-American Health Organization (Paho).” (3)
1.More Than 100 Cases of Measles Reported in Utah and Arizona, By Teddy Rosenbluth, https://www.nytimes.com/2025/10/21/well/more-than-100-cases-of-measles-reported-in-utah-and-arizona.htm
2.Measles spreading beyond the center of the Utah-Arizona outbreak, By Erika Edwards, https://www.nbcnews.com/health/health-news/measles-spreading-utah-arizona-outbreak-vaccines-rcna238757
3.US anti-vax stance to blame for continent-wide surge in measles, say experts, by Constance Malleret, https://www.theguardian.com/global-development/2025/oct/17/health-infectious-diseases-vaccination-measles-us-robert-kennedy-latin-america-antivax-blamed-cases-deaths-rise
curated by Jonathan M. Metsch, Dr.P.H.
Clinical Professor of Environmental Medicine, Icahn School of Medicine at Mount Sinai