
Today in Morbidity and Mortality Weekly Report, researchers in Wisconsin show how during the 2022-23 respiratory diseases season, high concentrations of influenza A virus and respiratory syncytial virus (RSV) in wastewater samples in three Wisconsin cities preceded virus-associated emergency department (ED) visits.
The authors say the study provides more evidence that wastewater surveillance can detect viral signals earlier than other surveillance methods.
Samples from 40 treatment plants
Wastewater testing rose in prominence during the COVID-19 pandemic, as detections accurately predicted spikes in viral activities in communities. In the present study, researchers collected wastewater samples from 40 treatment plants in Wisconsin’s biggest cities—Milwaukee, Madison, and Green Bay—at least once per week from August 2022 through March 2023.
ED visit data was linked to patients with a Green Bay, Madison, or Milwaukee residential zip code. A total of 6,271 flu-associated ED visits and 1,518 RSV-associated ED visits were reported from August 2022 to March 2023.
Wastewater surveillance might help supplement established clinical surveillance for these viruses.
The authors found a positive correlation between wastewater surveillance and ED visit data, with detections increasing in the 1 to 2 weeks before a rise in clinical cases was observed. Moreover, viral shedding occurred in wastewater samples for up to 3 weeks after the viruses peaked in communities.
"RSV peaked in early November, and influenza peaked approximately 1 month later," the authors wrote. "The positive correlation between wastewater surveillance and ED 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."