Wastewater Monitoring: Influenza and Respiratory Syncytial Virus (RSV) Levels in Wastewater

This interactive dashboard includes the following sections:

Description	Sections
A legend with concentration levels categorized by color. See Definition and methods below for more information.
A heat map (colored squares) on the dashboard show the concentration category or level of influenza A, influenza B, and RSV for each location.
A scatter plot showing the selected location's weekly concentration values and categories over time.
A map of Wisconsin with a circle of the selected location, showing the weekly concentration category.

Sewershed: 

An area of land where raw sewage from homes and businesses flows through a series of sewer pipes into a single downstream point, where it enters a wastewater treatment facility. The terms sewershed and location are used interchangeably on the wastewater pages with a given sewershed representing a location.

Processing time:

Dates on the graph indicate the day that the sample was collected at the treatment plant. With shipping and processing time, it typically takes five to 10 days for data to be included on the dashboard.

Category: 

The heatmap (colored squares) on the dashboard show the category of influenza A, influenza B, or RSV levels in each location.

When a wastewater sample is tested for a given virus, the test shows how much viral ribonucleic acid (RNA), gene copies per liter of sewage, is present in that wastewater sample. These levels (called raw concentration) are “normalized” to adjust the final result for the number of people in the population and the amount of sewage that flows through that facility each day. When multiple samples are sent in a given week, we calculate the average concentration of each virus over a week in each location. Each location’s weekly average is compared to the baseline levels that are expected from that site (the range of all levels measured from a given site using the current laboratory method), and are assigned the following categories:

• 67th-100th percentile (high)
• 33th-66th percentile (moderate)
• 1th-33th percentile (low)
• 0 (not detected)

The current category displayed on the dashboard for each site indicates how recent levels at that facility compare to the historical range of concentrations from that site.

The length of the reference period used to determine the cut-off levels for each category depends on the laboratory method used and how long the facility has been submitting samples.

For each location

The location level, shown both in the center chart with color-coded squares and as a scatter plot (line with circles), represents influenza A, influenza B, or RSV levels in a selected location over time. The circles represent individual samples that were collected, and its color represents the categorization (not detected, low, medium, high). The categorization for each individual sample is calculated as described above (current level compared to all historical data in that site). The black line is a smoothed spline, or a curve, that is used to display the data’s pattern over time.

The level of influenza A, influenza B, and RSV at a given site indicates the average amount of these viruses detected in samples from that site in the past week compared to all levels measured at that site over time. A higher level indicates that more virus is circulating within a given location.

• A “High” level means that the amount of virus circulating in your location is higher than usual, and you should take precautions to protect yourself from flu and RSV such as those listed.
• A “Moderate” level means that levels are comparable to what may typically be detected during a flu season. Moderate levels still indicate flu and RSV activity, and you should consider preventative measures.
• A “Low” level means that levels are lower than during a typical flu season and could indicate that there is little or no flu activity in your location.
• A “Not detected” means that no virus was detected in a sample.

Wastewater levels should be interpreted alongside other established public health data (see DHS Respiratory Dashboard) in order to provide a complete picture of respiratory disease activity in Wisconsin. Even when respiratory illness levels are low to moderate, it is important to keep up with prevention strategies. Follow these tips to help keep you and your loved ones healthy:

• Stay up-to-date with vaccines.
• Take steps for cleaner air, such as gathering outside or bringing in outside air.
• Wash your hands and practice good hygiene.
• Cover coughs and sneezes.
• Stay home if you are sick.

Additional precautions, such as wearing a mask and physical distancing, should be considered when illness levels are moderate or high. If you or people around you have risk factors for severe illness, consider additional precautions at any time.

We are still learning about wastewater levels and what they mean for communities. It is not possible to determine the exact number of people infected with a given virus based on wastewater levels alone. Therefore, it is more important to look at the category (not detected, low, medium, high) and the direction (increasing or decreasing) of wastewater levels in your location, not the total number of gene copies in the results. The data in the dashboard shows the total number of viral gene copies detected in the area from which the wastewater was collected.

Can I compare results from one location with another?

We do not recommend comparing results between communities. Each location or sewershed’s wastewater is different. For example, some have discharge from industrial sources and varying amounts of rainwater which affects viral concentrations differently. It is better to use data from a single location to see trends over time. However, you may compare trends between different locations.