More measles infections have been reported this year in the United States than in any year in more than three decades, with 1,356 confirmed cases from 42 counties by mid-August, notes a report featuring a daily county-level case map and state-level epidemic curves published yesterday in JAMA.
Before the measles vaccine became available in 1963, over 90% of US residents were infected by the virus before they were 15 years old, with the 3 million to 4 million annual infections leading to about 48,000 hospital admissions.
But after the vaccine was rolled out, national efforts to end local measles transmission through increased vaccination in school-aged children, surveillance, and outbreak control officially eliminated endemic measles in 2000, the Johns Hopkins University (JHU)–led research team noted.
“From 2000 to 2024, annual US measles infections averaged less than 200,” they wrote. “The surge in measles cases since 2020 also coincides with declining vaccination coverage in the US, further increasing the risk of measles outbreaks and threatening the US’ current endemic elimination status.”
County-specific reporting protocols
Because measles outbreaks are often localized, they can only be meaningfully captured with more granular data than the national- and state-level information that the Centers for Disease Control and Prevention (CDC) publishes, the researchers said.
To address this surveillance gap, the investigators developed a national data collection and reporting infrastructure that provides near–real-time, county-level measles case data beginning in January 2025, and shared via a public dashboard and open data repository since May.
County-level imported and community-acquired measles cases and demographic data are collected twice a week from state and local public health department websites, dashboards, news releases, and public health bulletins.
To address heterogeneous reporting and inconsistencies in the frequency and timing of reporting, different reporting formats and media, and the variables reported, the team created county-specific protocols tailored to data formats and reporting schedules.
Informing public health interventions, vaccination efforts
The measles dashboard features national maps with county-level cumulative and recent 2-week case counts, a table summarizing these data at county and state levels, and cumulative and weekly nationwide incidence curves for 2018 to 2025. It also provides state-level cumulative and weekly incidence curves for the hardest-hit states, such as Texas, as well as nationwide vaccination status and age-groups for all confirmed cases.
The infrastructure was built upon established principles from JHU’s COVID-19 tracking experience to standardize heterogeneous surveillance data while maintaining comprehensive coverage and data quality through systematic validation protocols.
“By centralizing information from diverse jurisdictional reporting systems, this data collection and sharing infrastructure provides timely and actionable situation awareness for measles and may help to inform public health interventions and vaccination programs within communities as well as model more precise outbreak risk,” the authors wrote.
“The infrastructure was built upon established principles from JHU’s COVID-19 tracking experience to standardize heterogeneous surveillance data while maintaining comprehensive coverage and data quality through systematic validation protocols,” they added.
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