[{"model": "dashboard.pathogendescription", "pk": 3, "fields": {"pathogen": "Influenza", "lead_text": "Samples are collected at wastewater treatment plants from across the state and analyzed at our lab in Chicago. Results are posted and updated weekly. Numbers on the y-axis represent influenza A/B viral remnants in gene copies/liter. Dates on the x-axis are dates the samples were collected.", "details": "

Interpreting results

Wastewater surveillance data is "noisy," meaning it is highly variable. Samples are taken from sources (i.e. wastewater treatment plants) that are subject to a variety of environmental impacts, including weather events and industrial activity. For this reason we focus on increasing and decreasing trends in the data rather than specific measurements. A significant increase over time may indicate cases are increasing in a community.

Wastewater surveillance data should always be interpreted alongside other public health metrics.

Why are there two different colored data points?

The different colored data points represent two different types of influenza, types A and B. Influenza A and B are the most common types of influenza viruses that infect humans and cause seasonal epidemics, and thus are of importance for public health.

What does the line mean?

Since wastewater data are highly variable, we include a curve fitted to the data to better visualize increases and decreases. We do this by "smoothing" the data using the Locally Weighted Scatterplot Smoothing (LOWESS) method, a local regression analysis. This method is useful because it reduces the influence of data outliers (i.e. sample readings that are much higher or much lower than the other samples taken at the same site during the same general time frame). We also include 95% confidence intervals around the trend line. This means we are 95% certain the actual trend line is within the intervals.

What is the difference between log and linear?

A linear scale uses an equal distance between steps on the vertical axis, adding a constant number for each new step (e.g., 1, 2, 3, 4 or 10, 20, 30, 40). A log scale uses an unequal distance between steps, multiplying by a constant number for each new step. Typically, as we do here, this multiple is 10, so the axis might show steps at 1, 100, 1000, 10,000, etc.

Log scales are used to visualize data when the range of values shown is large and when viewing data over a longer time period. Public Health officials and scientists often work with data on these scales, while linear scales are more familiar to the general public.

Limitations of the data

Researchers are still working on understanding many open scientific questions, including how to use the data to tell how many people are sick. Variability between wastewater sources, treatment facilities, and communities makes it difficult to translate the influenza A/B gene copy (gc) concentration into a measure of how many people are infected in the community. However, an upward/downward trend in influenza A/B gc/liter generally suggests a similar trend in the number of people infected within a given community.

For similar reasons related to the variability in each sample, comparing data from site-to-site is also discouraged.

Methodology

Wastewater is analyzed using the GT-Digital Influenza and SARS-CoV-2 Wastewater Surveillance Multiplex Assay Kit for the QIAcuity® Digital PCR System, which comprises of a molecular reagent kit containing all primers, probes, and controls for wastewater surveillance of Influenza and SARS-CoV-2. The kit complies with the CDC Wastewater Surveillance Testing Method guidance for reporting to the National Wastewater Surveillance System (NWSS). Results are reported in gene copies per liter (gc/L) of starting wastewater.

References

Armbruster, D.A. et al., Limit of blank, limit of detection and limit of quantitation, Clin. Biochem. Rev. 29, Suppl 1, 2008

"}}, {"model": "dashboard.pathogendescription", "pk": 2, "fields": {"pathogen": "SARS-CoV-2", "lead_text": "Samples are collected at wastewater treatment plants from across the state and analyzed at our lab in Chicago. Results are posted and updated weekly. Numbers on the y-axis represent SARS-CoV-2 viral remnants in gene copies/liter. Dates on the x-axis are dates the samples were collected.", "details": "

Interpreting results

Wastewater surveillance data is "noisy," meaning it is highly variable. People infected with SARS-CoV-2 shed the virus at different levels of intensity and for different lengths of time. Samples are also taken from sources (i.e. wastewater treatment plants) that are subject to a variety of environmental impacts, including weather events and industrial activity. For this reason, we focus on increasing and decreasing trends in the data rather than specific measurements. A significant increase over time may indicate cases are increasing in a community.

Wastewater surveillance data should always be interpreted alongside other public health metrics.

Why are there two different colored data points?

We made a change to our lab methods in February 2022 to improve our ability to detect very small quantities of virus in wastewater. Our new method increases the amount of virus we are able to extract from each sample. Because wastewater contains more than just viruses (chemicals, food scraps, soaps, human waste, etc.), it can be tricky to isolate the viruses we are looking for. The new method helps us do just that.

Data generated with the previous method is not directly comparable with the new method.

What does the line mean?

What is the difference between log and linear?

Limitations of the data

Researchers are still working on understanding many open scientific questions, including how to use the data to tell how many people are sick. Variability between wastewater sources, treatment facilities, and communities makes it difficult to translate the SARS-CoV-2 gene copy (gc) concentration into a measure of how many people are infected in the community. However, an upward/downward trend in SARS-CoV-2 gc/liter generally suggests a similar trend in the number of people infected within a given community.

For similar reasons related to the variability in each sample, comparing data from site-to-site is also discouraged.

Methodology

Wastewater is analyzed using digital polymerase chain reaction (dPCR) to determine the concentration of the SARS-CoV-2 virus in a sample. The nucleocapsid protein (N) gene of the virus is targeted in the assay, and results are reported in gene copies per liter (gc/L) of starting wastewater.

References

"}}, {"model": "dashboard.pathogendescription", "pk": 4, "fields": {"pathogen": "RSV", "lead_text": "Samples are collected at wastewater treatment plants from across the state and analyzed at our lab in Chicago. Results are posted and updated weekly. Numbers on the y-axis represent respiratory syncytial virus Illness (RSV) viral remnants in gene copies/liter. Dates on the x-axis are dates the samples were collected.", "details": "

Interpreting results

Wastewater surveillance data is "noisy," meaning it is highly variable. Viruses are shed from infected individuals at different levels of intensity and for different lengths of time. Samples are also taken from sources (i.e. wastewater treatment plants) that are subject to a variety of environmental impacts, including weather events and industrial activity. For this reason, we focus on trends in the data rather than specific measurements, specifically increases and decreases. A significant increase over time may indicate cases are increasing in a community.

Wastewater surveillance data should always be interpreted alongside other public health metrics.

Why are there two different colored data points?

The different colored data points represent two different types of RSV, types A and B. RSV A and B are the most common types of RSV viruses that infect humans and cause seasonal epidemics, and thus are of importance for public health.

What does the line mean?

What is the difference between log and linear?

The linear scale uses an equal distance between steps on the vertical axis, adding a constant number for each new step (e.g., 1, 2, 3, 4 or 10, 20, 30, 40). A log scale uses an unequal distance between steps, multiplying by a constant number for each new step. Typically, as we do here, this multiple is 10, so the axis might show steps at 1, 100, 1000, 10,000, etc.

Limitations of the data

Researchers are still working on understanding many open scientific questions, including how to use the data to tell how many people are sick. Variability between wastewater sources, treatment facilities, and communities makes it difficult to translate the RSV A/B gene copy (gc) concentration into a measure of how many people are infected in the community. However, an upward/downward trend in RSV A/B gc/liter generally suggests a similar trend in the number of people infected within a given community.

For similar reasons related to the variability in each sample, comparing data from site-to-site is also discouraged.

Methodology

Wastewater is analyzed using the GT-Digital RSV Wastewater Surveillance Kit for the QIAcuity® Digital PCR System, which comprises of a molecular reagent kit containing an assay solution and control required for the quantification of respiratory synctial virus (RSV). The nucleocapsid gene is targeted. Results are reported in gene copies per liter (gc/L) of wastewater.

References

Armbruster, D.A. et al., Limit of blank, limit of detection and limit of quantitation, Clin. Biochem. Rev. 29, Suppl 1, 2008

"}}]

Princeton Sewage Treatment Plant