Measles quietly spread across the American Southwest in the spring of last year. But New Mexico health officials detected an alarming signal not in hospitals or clinics, but deep inside the state’s wastewater system.
Five days before the doctors confirmed the measles cases in Sandoval County, traces of the highly contagious virus had already appeared in sewage samples collected by public health researchers. The discovery served as an early warning, allowing the state to mobilize vaccines, alert hospitals, and prepare outbreak response teams before patients even sought medical care.
Wastewater sounds the alarm
In a study, Kelley Plymesser of the New Mexico Department of Health, in collaboration with federal health officials and researchers at Rice University, examined the growing role of wastewater surveillance as a public health tool in an era of resurging infectious diseases.
“It did exactly what it was supposed to do,” Plymesser said. “It gave us an early-warning system, particularly in areas where there were no reported cases yet.”
The findings came as the United States faces its largest measles outbreak in decades. Outbreaks have spread to 45 states since January 2025. The outbreak has alarmed epidemiologists who warn that the nation’s elimination status — declared in 2000 after years of widespread vaccination campaigns — is at risk.
Between February and September 2025, New Mexico recorded its first measles outbreak in nearly three decades. One of the 100 confirmed cases is linked to outbreaks in neighboring West Texas counties, part of a regional spread eventually reaching 31 states.
New Mexico responded to the outbreaks by expanding its wastewater monitoring system, which first gained prominence during the COVID-19 pandemic. Public health officials for a period covering March through August 2025 collected weekly untreated sewage samples from nine wastewater treatment plants across six counties, namely: Bernalillo, Chaves, Doña Ana, Luna, Sandoval, and Santa Fe. The Stadler Laboratory at Rice University analyzed the samples, which returned results to the state within 10 days.
Measles spreads before its symptoms appear
Then the surprise came. In May 2025, while Sandoval County and its neighboring counties had documented zero measles cases, wastewater in the area tested positive for measles. Five days later, hospitals confirmed several measles cases.
The lead time proved critical for public health officials because measles can spread days before symptoms appear, making traditional case tracking reactive. The detection of measles in wastewater allowed officials to pre-position vaccines, notify medical providers, and dispatch outbreak teams before the virus could further spread.
“That five-day window gave us time to plan and mobilize,” Plymesser said. “It gave us more time to prepare.”
Scientists increasingly consider wastewater epidemiology as one of the most promising tools for monitoring infectious diseases. The wastewater, according to public health officials, captures viral activity across entire communities, including among people who did not seek testing or treatment.
The method has limits, however. About 30 percent of New Mexico residents rely on septic systems, which make centralized wastewater monitoring impossible. While sewage monitoring can reveal community spread, it cannot identify who got infected.
Despite the limitation, state officials say the program is likely to expand. The Centers for Disease Control and Prevention has funded New Mexico’s wastewater surveillance initiatives through 2027, with grant support until 2029. Officials say they are expanding the number of pathogens they track as concerns grow over future outbreaks.
In 2026 so far, Brant reported that New Mexico has reported 15 measles cases. Health officials have not reported any new cases since March.
The message from the sewage system was unmistakable to health officials. And that is by the time hospitals treat measles, the virus may already be several steps ahead.