Thanks to successful childhood immunization programs, measles was uncommon in the U.S. for many years. However, cases do occasionally arise when travelers bring the virus from abroad, infecting unvaccinated individuals, especially children.
These cases are no longer isolated incidents. Due to a sharp decline in vaccination rates across the U.S., partly fueled by anti-vaccine attitudes, measles cases are increasing. The CDC reports that in 2025, there have been outbreaks in 33 states. (In comparison, only 16 outbreaks were reported throughout 2024.)
Scientists may now have discovered a novel method for identifying cases. Researchers have recently published data on locations where the measles virus is appearing in wastewater.
Wastewater surveillance is a valuable public health resource because it offers an unbiased view of where a particular virus is causing infections, often before standard testing methods can. It can provide a crucial early warning to health officials for viruses like measles, which infected individuals shed in their urine, feces, or saliva. Dr. Marlene Wolf, assistant professor at Emory and principal investigator and co-program director of , an academic and commercial group that includes researchers from Stanford University, Emory University, and Verily (Alphabet Inc.’s research organization), explains that it provides a “finger-to-the-wind weather map” of infectious disease activity.
Here’s what wastewater analysis is revealing about measles in the U.S.
Adding measles to the menu of wastewater tests
WastewaterSCAN began screening sewage in the U.S. for the COVID-19 virus in 2020. Since then, it has expanded to include other disease-causing microbes, such as influenza, RSV, human metapneumovirus (HMPV), norovirus, enterovirus, mpox, Candida auris, and hepatitis A.
This spring, the scientists started working on a test to detect the active or “wild type” measles virus responsible for outbreaks in the U.S. The test uses samples collected from nearly 150 sewage sites nationwide and can detect measles indicators within 48 hours.
To date, the virus has been detected at three sites: one day in Hollywood, Md.; four days in late May in Sacramento; and twice in mid-May in Stamford, Conn. WastewaterSCAN is just one wastewater surveillance network in the U.S., though it is the first to test for measles on a national scale. The CDC established its in 2020, encompassing over 1,400 sites that serve 150 million Americans. Some state health departments, including Texas, where the recent measles outbreaks originated, are also testing wastewater samples. WastewaterSCAN is working with the CDC, but the CDC is not yet testing wastewater for measles.
Why wastewater monitoring may be especially useful for measles
Doctors are required to report measles cases to the CDC, which allows the agency to track and respond to outbreaks. However, there is a delay between when people develop symptoms, seek medical attention, get tested, and when the case is reported if positive. Moreover, early measles symptoms are common, such as fever, runny nose, and cough, occurring before the characteristic rash. Furthermore, some individuals may not become ill enough to realize they have measles, leading to unreported cases. Others may be sick but lack access to medical care, preventing them from seeking help.
Wastewater monitoring circumvents these obstacles, potentially detecting the virus much earlier. This could be particularly beneficial for a highly contagious disease like measles, where a single infected person can quickly transmit the virus to as many as 18 others. According to Wolfe, this anonymous testing combines data from everyone in a community, and with measles, the virus is likely shed into wastewater before people realize they are infected.
How wastewater data can help health officials
Wolfe indicates that it is still too early to determine whether this measles tracking method can detect cases in a region before positive test results become available. However, wastewater surveillance was successful in identifying the COVID-19 virus before cases started appearing in hospitals and testing facilities.
As more measles data is gathered, health experts can start identifying trends and patterns, such as increases in the number of positive samples. This could enable public health departments to focus resources, like vaccines, on areas where infections are spreading. Declining numbers of positive samples could also alert them when infections are coming under control.
What to do if cases are detected near you
Vaccination is the most effective way to prevent measles infection, providing near-lifelong immunity. Ensuring that all eligible individuals are current on their measles vaccinations can help them avoid infection.
“`
