There must be something in the water in Houston.
The city is home to a Centers for Disease Control and Prevention (CDC) National Wastewater Surveillance System of Excellence, and UTHealth Houston hosts a public health partnership that helps detect infectious disease outbreaks by testing wastewater from a constellation of 15 cities spanning the state. These organizations push the country’s fourth-biggest city to the forefront of technology that helps warn the public about disease outbreaks.
“Across the country, different states and health departments are at different stages of acquiring and implementing this technology,” said Rama Thyagarajan, MD, MPH, a member of the Texas Medical Association’s Committee on Infectious Diseases. “The Houston Department of Health is a leader in wastewater monitoring.”
Wastewater-based epidemiology, employed in polio eradication efforts since at least the 1970s, gained fresh relevance during the COVID-19 pandemic. As vaccination and immunity rates improved, making illness milder, and with the advent of home testing, many cases of infectious disease went unreported. Wastewater emerged as a reliable gauge to track viral peaks in a population.
Effluent sampling yields public health data that doesn’t require reporting by physicians or self-reporting by patients, and it captures the presence of virus even in those without symptoms or access to health care. Those data can help health infrastructure prepare for viral spikes and waves and reflect the efficacy of vaccines. Advances in the past few years to the technology that supports wastewater sampling have enhanced its scalability and the granularity of the data it garners, making it a key epidemiological alarm bell to curb disease waves, such as the spring spread of measles in Texas.
“The canary in the coal mine” is how Desmar Walkes, MD, describes it. The Austin-Travis County health authority and medical director for Austin Public Health says wastewater sampling data can be a tool for expanding public health entities’ field of vision.
“Being able to test what is in our sewage system gives us some visibility on what it is that might be coming our way, might be trending in our community, and what we, in some instances, need to start preparing for,” the chairperson of TMA’s Public Health Committee said.
A finer resolution
Like Houston Wastewater Epidemiology, one of just six CDC-endorsed centers in the U.S., Texas Epidemic Public Health Institute (TEPHI) has its own accolades. The institute funded a study by researchers at one of its partner organizations, Baylor College of Medicine, that won the popular vote in last year’s STAT Madness, a bracket-style competition sponsored by the namesake health and medicine publication in which 64 biomedical research teams participated.
The Baylor team, led by Anthony Maresso, PhD, and Michael Tisza, PhD, identified 465 viruses in wastewater using genome sequencing. Their work on the topic was voted by STAT readers as among the most important and impactful health research published in the year leading up to March 2024.
TEPHI implemented the technology undergirding that tournament win – agnostic testing, a diagnostic that can detect any pathogen – in TexWEB, the Texas Wastewater Environmental Biomonitoring program it administers along with partners UTHealth Houston School of Public Health, Baylor College of Medicine, and El Paso Water.
“We are actually using a totally different technology [compared to traditional polymerase chain reaction (PCR) or real-time PCR testing] to sequence the entirety of the genomes of all known mammalian viruses – there are more than 3,000 of them – and allow us to go through and do this all in one reaction,” said Blake Hanson, PhD, an epidemiologist at UTHealth Houston who works with TEPHI. “[For example], with the emergence of H5N1 again in cattle, we were able to identify multiple locations across the state, find H5N1 in our wastewater, and show that it was exactly the same strain that was circulating in cattle. It allows us to take a totally different scope and look at everything.”
The scalability of that technology is its most meaningful advance and advantage over PCR testing, Dr. Hanson says.
“There’s only so far PCR scale [can go] before it becomes very challenging and also very expensive, whereas everything we do is within a single reaction, and it covers every virus that we know of,” Dr. Hanson said. “[It] gives us that much finer resolution where we can say exactly what variants of these viruses we’re seeing circulating, what’s changing, and have that different level of interrogation.”
Catherine Troisi, PhD, a UTHealth Houston epidemiologist who also works with TEPHI, recommends that physicians monitor the TexWEB dashboard to keep abreast of what’s circulating locally to inform their practice.
“Citing Texas’ measles outbreak, for example,” she said. “If we started to see a lot of measles in the wastewater, when somebody comes in with a rash – a lot of doctors haven’t seen measles, younger or even middle-aged doctors – that might make them think oh, maybe I should think about measles in this case. And that’s true for other diseases as well.”
Drs. Troisi and Hanson commend the public health departments that help facilitate TEPHI’s work, describing the network of stakeholders who share wastewater data as a massive partnership among many parties across the state. And Dr. Hanson notes many partners have made progress integrating wastewater data into their communications streams, taking some burden off physicians to find the information.
Supplementing the armamentarium
Dr. Thyagarajan notes wastewater sampling supplements the full complement of public health tools to detect and identify pathogens in a community.
“Public health departments, experts, and personnel use a lot of tools in their armamentarium to guide clinicians, health providers, health systems, commercial labs, and the public,” she said.
In places where there is functioning wastewater monitoring, Dr. Thyagarajan says there’s a good setup for not only detecting COVID-19, but also other viruses, such as RSV, influenza, and mpox. (See “A Growing Network of Data Points,” page 39.)
As of this writing, TMA’s Committee on Infectious Diseases, to which Dr. Thyagarajan belongs, is developing CME in podcast form pertaining to wastewater sampling, including how best to use the data it yields and how to apply it to emerging threats. The committee plans to collaborate with TEPHI and the Houston Health Department.
Dr. Thyagarajan also sees the need for guidance on interpreting wastewater testing results, which can sometimes appear in unintuitive formats.
“[When] it’s reported in viral copies and percentages, this can be confusing to health providers,” she said. “The transparency needs to continue, but guidance on proper use of the test results needs to be in the forefront of what health departments do.”
She added “more momentum is needed” in the state to increase funding for local health departments and raise physicians’ awareness of wastewater testing as a public health and preparedness tool.
Users of the TexWEB dashboard, which is available free to the public, select from a dropdown menu which pathogen they’d like to see the most recent wastewater data for and can further refine the results by selecting specific cities to view or, inversely, deselecting all cities and choosing overview thresholds (tma.tips/TEPHI Dashboard).
“This is something that we’re trying to make available to everybody at the community level – physicians, public health practitioners, anyone that may be out there – trying to make sure that they all have access to this information,” Dr. Hanson said.
TMA affirms this stance, especially knowing new viruses are an inevitability, and shares in TEPHI’s desire to spread the word about the value of data siphoned from wastewater.
“There’s going to always be some ongoing emerging viruses for a variety of reasons – climate change, significantly mobile populations, and global travel to name a few,” Dr. Thyagarajan said. “This passive monitoring is a valuable public health addition. We want TMA members to know about and support this tool and support public health departments acquiring [it].”