The United States reported 1,356 confirmed measles cases across 42 jurisdictions as of August 12, 2025, the highest annual total in more than three decades. To address the rise, researchers released a public county-level measles tracker that began collecting near–real-time data on January 1, 2025.
The tool launched on May 28, 2025, and provides twice-weekly updates of confirmed cases by county. Information includes vaccination status and age when reported by state and local health departments. Sources include jurisdictional websites, dashboards, press releases, and bulletins. For validation, the data are compared with national counts from the Centers for Disease Control and Prevention (CDC).
US measles surveillance data have historically been provided by the CDC at the national and state levels on a weekly basis. "Measles outbreaks are often highly localized and can only be meaningfully captured with more granular data," wrote lead researcher Farzin Ahmadi, PhD, of Johns Hopkins University, and colleagues.
The dashboard displays national maps with cumulative and 2-week county totals and distinguishes imported from local cases. A table lists county and state counts, and time-series graphs show national cumulative and weekly incidence trends from 2018 through August 2025. Separate epidemic curves are provided for the most affected states. The tracker also summarizes vaccination status and age distributions, and users can download county-level case series, state epidemic curves, and documentation via a linked repository.
Historical data underscore the severity of the increase. Before measles vaccination in 1963, an estimated 3 million to 4 million cases occurred annually in the United States, with about 48,000 hospitalizations. Endemic transmission was declared eliminated in 2000, and from 2000 to 2024, annual measles cases averaged fewer than 200. The 2025 increase coincided with declining vaccination coverage.
The study noted limitations: Potential inaccuracies may arise from inconsistent reporting across jurisdictions—especially for imported cases and reporting timelines. Future iterations could address these issues by partnering directly with health departments.
Disclosures: Funding support came from Bloomberg Philanthropies, which had no role in the study design, data collection, analysis, or publication. No conflicts of interest were reported.
Source: JAMA
