Measles is returning to communities in the United States where vaccination coverage has declined, challenging clinicians and laboratory professionals who may never have encountered a case. Here, Jennifer Horney, Professor and Founding Chair of the Department of Epidemiology at the University of Delaware, discusses the diagnostic clues, reporting requirements, and surveillance systems needed to identify infections quickly and limit further spread.
What's driving the recent rise in measles outbreaks across the US?
The increase in measles cases in the US is directly related to declining vaccination coverage. Because measles is highly contagious, people who are unvaccinated or only partially vaccinated face a high risk of infection following exposure. Although vaccination rates have declined only slightly nationwide, coverage is considerably lower in some communities. This includes the West Texas community where the 2025 outbreak began, which had a vaccination rate of approximately 80 percent.
What are the biggest diagnostic challenges with measles today, especially since many physicians and laboratorians have never encountered a case?
Although many health care professionals have not encountered measles during their careers, the disease typically presents with high fever, conjunctivitis, and a characteristic rash. Given the current number of cases in the United States, clinicians may also be more alert to possible infections. Initial screening should include the patient’s vaccination status and any known exposure to a person with measles, as these factors can indicate an increased risk of infection.
Are there any current concerns about measles testing?
No; even after the United States achieved elimination status, isolated outbreaks continued to occur, often following travel-related introductions or within communities with low vaccination coverage. Suspected measles cases must be reported immediately to public health authorities, and established testing and surveillance systems are in place.
How can laboratories help improve outbreak surveillance and ensure cases are identified and reported quickly?
Because measles spreads rapidly – one person can transmit the virus to as many as 18 susceptible people – clinicians are legally required to report suspected cases immediately to the appropriate public health department. Reporting should not be delayed while awaiting laboratory confirmation.
What can molecular testing and genotyping tell us about how outbreaks spread, and how important are these tools for public health?
Connecting cases through their “genetic fingerprints” can help public health authorities trace the spread and source of infectious diseases. During a foodborne outbreak, for example, matching DNA patterns in patient and food samples may identify a common source, allowing officials to implement control measures such as product recalls.
Looking ahead, what changes in laboratory preparedness or public health infrastructure are needed to better respond to future measles outbreaks?
When public health systems work well, their impact often goes unnoticed. As a result, funding may increase during emergencies and decline once the immediate threat has passed, putting the capacity developed during the response at risk. Sustaining an effective response requires continued investment in public health professionals who are trained to communicate clearly, address misinformation, and build community support.
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