Chlamydia trachomatis inclusion bodies (brown) in a McCoy cell culture. Credit: CDC
Wastewater-based disease monitoring dates back to polio surveillance in the 1940s and expanded significantly during the COVID-19 pandemic, but American public health agencies don't currently apply the method to STIs.
Now, researchers at the University of Washington have identified a method that could be used to identify Chlamydia trachomatis, the bacteria that causes chlamydia.
“STIs are known for being underreported because of a lot of factors, especially stigma and the prevalence of asymptomatic cases,” said co-lead author Erica Fuhrmeister, assistant professor of environmental and occupational health sciences and of civil and environmental engineering at the UW. “Wastewater is cool because it’s population level. You don’t need people to go to the doctor and seek out treatment to know that there are people in a community shedding specific pathogens.”
For their study, published in ACS ES&T Water, researchers collected frequent wastewater samples from five treatment plants across Washington state and six neighborhood-level sewer sites near Seattle.
They then tested the samples for the pathogens that cause three common STIs: chlamydia, syphilis and gonorrhea. C. trachomatis was the most prevalent pathogen across all test sites. The bacteria that cause gonorrhea and syphilis were found far less frequently, despite data showing confirmed cases of those diseases in the associated areas.
In one notable example, a densely populated neighborhood site near a college campus—where more than 87% of residents were young people between 18 and 34, a group considered high-risk for STIs—showed very low chlamydia case counts in clinical health records, even though researchers consistently detected C. trachomatis in the wastewater itself.
The researchers say the gap between clinical case counts and wastewater detections could reflect underreporting driven by stigma or asymptomatic infection, and that the approach offers health officials a way to spot rising infection activity in a community even when it isn't showing up in clinics.
Data from University of Washington