Oregon Wastewater Surveillance

Washington County Public Health Use of Wastewater Surveillance Data Testimonial from Catherine Desmarais, DrPH, Communicable Disease Epidemiologist:

“As an epidemiologist, I utilize the wastewater data weekly when giving my review of respiratory disease trends in our county to our team. As many are aware, COVID testing behavior has changed significantly over the last five-and-a-half years. Most people now test for COVID in their homes, and those results are not reported to the state and thus are not counted in the weekly percent positivity calculations. Many people are not even testing at home if they have respiratory symptoms anymore. So overall, the percent positivity of COVID tests is a significant underestimate of circulating virus and old and new numbers are not comparable. This is where wastewater monitoring comes in and why it is so important to our team. It does not rely on testing behaviors or care seeking by cases and is consistent throughout the course of the pandemic. Wastewater gives us an estimate of the true burden of the disease regardless of outside factors. The wastewater data, when timely, provides context to the percent positivity numbers and is valuable to our planning processes seeing wastewater concentrations often rise before we see the associated increase in test percent positivity. For example, knowing that viral concentration is rising in local watersheds allows the team to shift workloads so they are better able to respond to respiratory outbreaks and provide resources to facilities in need of assistance in controlling their outbreaks. The inclusion of variant data also allows us to plan for case spikes when we see a novel variant reach ~50% of circulating variants. In summary, wastewater is by far the most consistent and accurate tool to estimate disease burden in the community and we use it regularly for monitoring, planning, and prevention purposes. As an aside, wastewater and variant data is also used in hospital and health system calls during the respiratory season for similar purposes.”