U.S. health officials are closely monitoring a concerning resurgence of measles cases, with infections rising in tandem with falling childhood vaccination rates. As of May, 14 measles outbreaks have been reported across 33 states, according to the Centers for Disease Control and Prevention (CDC)—nearly matching the total number of outbreaks in all of 2024.
Historically rare in the U.S. due to widespread immunization, measles cases have climbed in recent years amid growing vaccine hesitancy. Public health experts are now turning to a new detection method to help track the virus: wastewater surveillance.
This spring, researchers from WastewaterSCAN, a nationwide wastewater monitoring initiative led by Emory and Stanford Universities in partnership with Alphabet’s Verily, began testing sewage for measles virus RNA. The virus, which infected individuals can shed through urine, saliva, and feces, can be detected in wastewater up to two days after it appears in a community.
So far, signs of measles have been detected at three sites: Hollywood, Maryland; Stamford, Connecticut; and Sacramento, California. “It gives us a finger-to-the-wind weather map of what is happening with infectious diseases,” said Dr. Marlene Wolfe, assistant professor at Emory and co-leader of WastewaterSCAN.
The system samples from nearly 150 sewage sites nationwide, complementing other surveillance networks. While the CDC runs its own National Wastewater Surveillance System, covering 150 million Americans across 1,400 locations, it does not yet include measles testing. Some states, including Texas—where recent outbreaks began—conduct their own local wastewater monitoring.
Unlike traditional case reporting, which depends on individuals developing symptoms, seeking care, and getting tested, wastewater surveillance offers a faster and more anonymous method of detection. Given measles’ high contagion rate—one infected person can spread the virus to up to 18 others—early detection is crucial.
Symptoms often begin with fever, cough, and runny nose before progressing to a telltale rash. However, not all cases are reported, especially among those who don’t seek medical care or are asymptomatic. Wastewater testing helps fill that gap, potentially allowing public health officials to identify outbreaks early and direct vaccine resources accordingly.
While it’s too soon to know if this system can consistently predict outbreaks before clinical cases emerge, experts are optimistic. “For measles, it’s likely that shedding into wastewater is happening before people necessarily recognize what they have,” Wolfe noted.
Health officials continue to urge Americans to ensure their vaccinations are up to date, emphasizing that the measles vaccine offers nearly lifelong protection.
