LEONARDTOWN, Md. — A wastewater sample from St. Mary’s County tested positive for measles virus on May 16, 2025, as part of a national pilot study, WastewaterSCAN, conducted by Stanford and Emory universities. The study, which began monitoring wastewater for infectious agents in 2023, added measles testing in May 2025. Four subsequent samples from the Marlay Taylor Water Reclamation Facility showed no traces of the virus, and no confirmed measles cases have been reported in the county.
WastewaterSCAN tests samples nationwide to detect early signs of infectious diseases, including measles, which can be shed in the urine or feces of infected individuals. The program’s data, now publicly accessible on its online dashboard, helps public health officials identify potential outbreaks before clinical cases emerge. “Monitoring wastewater is a tool for early detection of emerging illness in a community and allows healthcare providers and public health agencies time to prepare before cases may be known or disease spreads,” the St. Mary’s County Health Department (SMCHD) stated.
The May 16 detection at the Marlay Taylor facility marked the first instance of measles virus in the county’s wastewater. SMCHD emphasized that no confirmed cases have been identified, suggesting the positive sample may indicate an isolated or undetected case. Measles, a highly contagious respiratory disease, spreads through coughing and sneezing and can be transmitted four days before symptoms appear. Symptoms include a fever above 101 degrees, runny nose, red or watery eyes, cough, and a characteristic rash that starts on the face and spreads downward.
SMCHD is urging residents to remain vigilant for measles symptoms and ensure their vaccinations are up to date. “Measles vaccine is the best protection for preventing measles infection,” the department noted. The health department offers vaccines to all community members, regardless of ability to pay, and has scheduled clinics to increase access. From July 29 to August 14, 2025, vaccines will be available every Tuesday and Thursday from 9:00 a.m. to 12:00 p.m. at Spring Ridge and Margaret Brent School-Based Health Centers (SBHCs). Additional clinics are set for August 23 and September 27, 2025, from 9:00 a.m. to 1:00 p.m. at the same locations, and on Fridays, September 5, 12, and 19, 2025, from 9:00 a.m. to 12:00 p.m. at the main health department in Leonardtown. Appointments can be made by calling 301-475-4330.
Measles symptoms typically appear 7 to 14 days after infection, starting with fever, runny nose, red eyes, and cough. Two to three days later, tiny white spots may appear inside the mouth, followed by a rash of flat red spots three to five days after that. SMCHD advises anyone noticing these symptoms to limit contact with others and contact their healthcare provider before visiting a medical facility. “If using an emergency department for care, call ahead to let the facility know of your concerns so preparations for your arrival can be made,” the department stated, noting this reduces the risk of exposing others.
The WastewaterSCAN initiative, launched in 2023, has expanded to include measles among other pathogens, providing a proactive approach to public health surveillance. St. Mary’s County’s participation underscores its commitment to early detection and prevention. SMCHD’s website, smchd.org/health-topics/infectious-disease/measles, offers detailed information on measles and vaccination options.
As the county continues monitoring, SMCHD encourages residents to verify their immune status with healthcare providers. The absence of confirmed cases and negative follow-up tests suggest the May 16 detection may not indicate widespread transmission, but vigilance remains critical given measles’ high contagiousness.