Tracking Measles Cases in the U.S.

Measles outbreaks have been reported in multiple states, raising concerns about continued spread, increases in hospitalizations and deaths, and loss of measles elimination status, highlighting the importance of measles vaccination and rapid detection and reporting of suspected and confirmed measles cases. 

Measles is a highly contagious disease spread primarily through the air when an infected person coughs, sneezes, or talks, releasing tiny droplets containing the virus. People infected with measles have fever and a red, slightly raised rash. Some people with measles develop complications like ear infections, pneumonia, diarrhea, or inflammation of the brain itself, encephalitis, which can cause brain damage. Severe measles can lead to hospitalization and even death. The best way to prevent contracting measles is through measles vaccination. Having a high percentage of people fully vaccinated against measles is the best way to prevent outbreaks, and is also the best way to protect people who cannot get measles vaccines, such as babies or people with cancer.

The maps above show the current geographic distribution of confirmed measles cases by county across the United States, with the largest outbreak seen in west Texas from which other outbreaks have spread. The cumulative cases map includes measles cases reported for each county in the United States since January 1, 2025, revealing the relative scale of the outbreaks across states. The recent cases map includes only those cases reported within the past two weeks, providing a near real-time view of active transmission or newly imported cases. Blue dots represent locally acquired cases while red dots represent imported cases from out of jurisdiction (out of state or out of country) travel. As indicated by the relative size of the blue dots, most of the reported cases are due to local transmission, with relatively few cases being imported. Of the imported cases, the vast majority occur in travelers returning from other countries with ongoing measles outbreaks.

In addition to the measles maps, the following table shows the cumulative number and recent measles case counts, and whether imported or locally acquired, for each county (and state) where confirmed measles cases were reported since January 1, 2025.

The time series below shows the increase in measles cases over time in the United States by year since 2018. The weekly cases chart displays the number of reported measles cases by month since 2019, highlighting the magnitude of the current outbreak relative to recent years. You can toggle between ‘Cumulative cases by year’ and ‘Weekly cases’ graphs.

Measles vaccination is the best way to prevent measles and stop outbreaks. We see this clearly by looking at the vaccination status of measles cases in the United States. Unvaccinated individuals or those with unknown vaccination status represent almost all reported measles cases. These outcomes are consistent with estimates that two doses of measles vaccine protects 97% of those vaccinated. 

Before the introduction of measles vaccine in the United States in 1963, measles was largely a disease of young children. But measles cases now occur across all age groups. After widespread use of measles vaccine, unvaccinated individuals are less likely to be exposed to measles virus when growing up because they are protected from encountering the virus by vaccinated people in their community. However, when measles outbreaks do occur, as now in the United States, these susceptible adolescents and adults can get measles. The chart below shows the distribution of measles cases by age group in the United States since January 1, 2025. Many cases are in school age children, but older adolescents are also getting measles.

This dashboard is updated weekly on Fridays, with intermittent updates as warranted. The data presented in the maps are compiled from official sources, including state and county health departments and additional county-level news releases or news articles. The data represent all laboratory-confirmed measles cases reported by public health authorities. The data exclude "probable cases", cases not yet laboratory-confirmed, and cases not publicly reported. All reported cases are categorized as local unless indicated otherwise by the reporting source. Data completeness and timeliness vary by reporting jurisdiction. Recent case counts may be incomplete and are subject to backward revision as investigations are completed. To access the data, data sourcing, data/image use and licensing, please refer to the project's Github repository. An extended description of the data collection methodology is described in this JAMA publication.

About This Project

The project is a collaborative, interdisciplinary effort conducted by a group of researchers at Johns Hopkins University who are tracking and modeling the risk of measles in the U.S. It reflects contributions from the Center for Systems Science and Engineering (CSSE) at the Whiting School of Engineering, the International Vaccine Access Center (IVAC) at the Bloomberg School of Public Health, and the Bloomberg Center for Government Excellence.
 
The team is led by Lauren Gardner, Shaun Truelove, and William Moss. 

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