AUSTIN (KXAN) — Austin Public Health (APH) already looks at wastewater to detect the prevalence of COVID-19, and may start to test for influenza and respiratory syncytial virus (RSV), according to APH chief epidemiologist Janet Pichette.

“It would be really great to add things like RSV, norovirus and influenza because then that kind of gives us an idea of when our flu season and other seasons start,” Pichette said. “We kind of have an idea with norovirus that we tend to get more gastrointestinal illness occurring in certain months. But we can get an idea of what the background is and kind of monitor the trends over the course of the year.”

Research on the effectiveness of such tests occurred between August 2022 and March 2023 in three Wisconsin cities. The results of that research were published in the Center for Disease Control and Prevention’s (CDC) “Morbidity and Mortality Weekly Report.”

“The positive correlation between wastewater surveillance and ED [emergency department] visit data for both influenza and RSV, along with the detection of the two pathogens in wastewater before increases in associated ED visits, suggests that wastewater surveillance might help supplement established clinical surveillance for these viruses,” the article’s authors write. “Incorporation of, and continued research into, the capabilities of wastewater surveillance might improve local public health agencies’ understanding of and response to seasonal respiratory virus disease outbreaks.”

The authors note that their study was limited in four ways:

  • homes using septic systems and with diapered children;
  • data was generated weekly;
  • study only looked at one respiratory illness season; and,
  • wastewater can differ between communities.

Currently, “clinical surveillance” (the reporting of cases to public health authorities) is the primary means for knowing the spread of an illness. However, these only pick up cases where a patient has sought medical attention, creating gaps in the data.

“Flu is not a reportable condition, so we have to use a bunch of different techniques to monitor what’s happening in the community,” Pichette said. “Some providers out in the community, some major large clinical spaces and providers that actually when they start seeing people with influenza like illness, they will begin to start reporting that information out to us.”

A limitation in wastewater surveillance is in the supply of tests to public health officials. Austin was one of several cities affected by a recent COVID-19 wastewater test shortage, Pichette said, which disrupted data gathering in September.

“We know that there’s significant underreporting [of COVID] out in the community. And that happens during flu season as well. We know there are a lot of people who are probably walking around with flu, but that we don’t know they have it,” Pichette said. “[Wastewater surveillance] has been a really great tool that we have at our disposal…to see what’s circulating within the community, the concentrations that are circulating, and what variants might be circulating.”