US Measles Cases Near 2,000 in 2025 as Multi-State Outbreaks Expand

The Centers for Disease Control and Prevention (CDC) has reported a total of 1,958 confirm cases as of December 16, 2025, reflecting sustained transmission across much of the country. Of these cases, 1,888 were reported by 43 US jurisdictions, while 24 cases occurred among international visitors. CDC data are updated weekly and include only laboratory-confirmed cases notified to the agency.¹

The majority of cases reported this year have been outbreak-associated. The CDC has documented 49 measles outbreaks in 2025, defined as three or more epidemiologically linked cases, with 88% of all confirmed cases (1,673 of 1,912) linked to outbreaks. By comparison, 16 outbreaks were reported in 2024, when 69% of cases (198 of 285) were outbreak-associated.¹

Children and adolescents account for a substantial proportion of infections. Among reported cases, 26% occurred in children younger than 5 years, 41% in individuals aged 5 to 19 years, and 32% in adults aged 20 years or older. Vaccination gaps remain prominent: 92% of cases occurred in individuals who were unvaccinated or had unknown vaccination status, while 7% occurred in individuals who had received one or more doses of the measles, mumps, and rubella (MMR) vaccine.¹

Clinical severity has also been notable. The CDC reports that 11% of measles cases required hospitalization (218 patients), with the highest hospitalization rate observed among children younger than 5 years (21%). As of December 9, three measles-associated deaths have been confirmed in the US in 2025.¹

CDC officials note that declining childhood vaccination coverage continues to increase outbreak risk. National MMR coverage among US kindergartners decreased from 95.2% during the 2019–2020 school year to 92.7% in 2023–2024, leaving an estimated 280,000 children potentially susceptible. Localized pockets of under-immunization allow measles, one of the most contagious viral diseases, to spread rapidly once introduced.¹

South Carolina: Outbreak Accelerates to 126 Cases

South Carolina health officials reported 126 confirmed measles cases as of December 12, 2025, marking an acceleration of an outbreak centered in the northwestern part of the state, according to a Reuters report. The state confirmed 15 new cases since December 10, most linked to known exposures.²

To limit transmission, the South Carolina Department of Public Health placed 303 exposed individuals under quarantine, while 13 infected patients were placed in isolation. Among the newly reported cases, 13 resulted from household transmission, one from a neighborhood contact, and one from an exposure source that remains under investigation.²

Vaccination gaps have been a defining feature of the outbreak. Of the 126 infected individuals, 119 were unvaccinated, three had received one dose of the MMR vaccine, one was fully vaccinated, and three had unknown vaccination status. Although South Carolina requires two MMR doses for school entry, vaccination coverage has declined. During the 2023–2024 school year, 92.1% of kindergarteners were fully vaccinated, down from 95% in 2019–2020, below the threshold generally required for community immunity.²

Utah: 115 Cases Reported With Evidence of Community Spread

Utah health officials have reported 115 confirmed measles cases among state residents in 2025, with 26 cases identified in the past three weeks, according to the Utah Department of Health and Human Services. Case counts reflect ongoing transmission across multiple local health jurisdictions and were most recently updated on December 9, 2025.³

Public health surveillance has identified measles virus detections in wastewater, suggesting broader community circulation beyond clinically confirmed cases. Recent wastewater samples detected measles virus in Davis County, Southwest Utah, and Utah County, with additional detections reported in the Bear River health jurisdiction prior to the most recent sampling. Health officials note that wastewater testing confirms viral presence but does not indicate how many individuals are infected.³

Utah has also reported numerous public exposure events, including emergency departments, urgent care centers, pediatric clinics, schools, childcare facilities, a university campus, retail locations, and entertainment venues. These exposures span late November through early December, prompting symptom monitoring periods extending into late December.³

In response to evidence of undetected community spread, Utah officials issued expanded vaccination guidance. The state recommends that infants aged 6 to 12 months receive an early, additional MMR dose, particularly if traveling or residing in areas with active measles transmission. Children aged 12 months or older may receive their second MMR dose earlier than age 4, provided appropriate spacing from the first dose.³

Arizona: 176 Cases Concentrated Along the Utah Border

Arizona health officials have reported 176 confirmed measles cases in 2025, as the state continues to experience an active outbreak along the Arizona–Utah border, according to the Arizona Department of Health Services. Data were last updated December 9, 2025 and include both outbreak-associated and non-outbreak cases. The outbreak has been largely localized to Mohave County, which accounts for 172 of the 176 cases, with four cases reported in Navajo County. Six measles-related hospitalizations have occurred, and no deaths have been reported.⁴

Vaccination gaps remain pronounced. ADHS reports that 97% of cases occurred in unvaccinated individuals, and 66% involved people younger than 18 years, underscoring pediatric vulnerability. Public health authorities have identified multiple exposure sites in retail establishments, hotels, concert venues, and food service locations across Coconino, Maricopa, and Mohave counties.⁴

Because of geographic proximity and overlapping transmission patterns, Arizona officials are coordinating closely with Utah public health authorities and directing clinicians and the public to consult state and CDC measles dashboards for updated regional information. Post-exposure prophylaxis with a measles-containing vaccine within 72 hours of exposure remains a key strategy to prevent or reduce disease severity.⁴

Connecticut: First Case Since 2021 Identified

Connecticut health officials confirmed the state’s first measles case since 2021 on December 11, 2025. The case involves an unvaccinated child younger than 10 years of age from Fairfield County who had recent international travel prior to symptom onset, according to the Connecticut Department of Public Health.⁵

The child developed symptoms consistent with measles, including cough, rhinorrhea, fever, and a characteristic rash that began on the head and spread across the body. Health officials noted that symptoms typically appear 7 to 14 days after exposure and emphasized the importance of early recognition to prevent further spread.⁵

State Public Health Commissioner Manisha Juthani, MD, said that 2025 may mark the loss of US measles elimination status, pending formal CDC determination. Although Connecticut had previously been among the few states without reported cases in 2025, Juthani noted that sustained transmission nationwide made local spread increasingly likely.⁵

Together, these state-level outbreaks underscore the CDC’s assessment that measles transmission in the United States remains widespread in 2025, driven largely by declining vaccination coverage and localized pockets of under-immunization. With sustained transmission ongoing in multiple regions, public health officials continue to emphasize early case identification, airborne isolation, contact tracing, post-exposure prophylaxis, and on-time vaccination as central tools to prevent further spread.

References

1.Measles Cases and Outbreaks. CDC. December 11, 2025. Accessed December 15, 2025. https://www.cdc.gov/measles/data-research/index.html

2.South Carolina measles outbreak accelerates as cases rise to 126. Reuters. December 11, 2025. Accessed December 15, 2025. https://apnews.com/article/measles-outbreak-south-carolina-utah-arizona-3bfc561ecc16d8e80175effdae0791d4

3. 2025 measles response. Utah Department of Health and Human Services. Updated December 9, 2025. Accessed November 15, 2025. https://epi.utah.gov/measles-response/

4. Measles. Arizona Department of Health Services. Updated December 9, 2025. Accessed December 15, 2025. https://www.azdhs.gov/preparedness/epidemiology-disease-control/measles/index.php

5. CT reports first measles case since 2021. Connecticut Public Radio. Updated December 12, 2025. Accessed December 15, 2025. https://www.ctpublic.org/news/2025-12-11/measles-outbreak-ct-first-case-vaccine