FAQ
How can I give feedback on this dashboard and ask questions?
Please email us at
COVID19@newcastlede.org
for all feedback and questions.
Why test for COVID-19 in wastewater?
The virus that causes COVID-19 is called SARS-CoV-2 and may be shed in the stool and/or urine of infected individuals. The virus can be detected at varying levels in the New Castle County sewer system. Sampling the sewer system provides insight into the health of the entire sewer shed population and is a cost-effective means of obtaining information on thousands of people at once. This information is important complementary information to clinical testing data. People who are presymptomatic or asymptomatic may still shed the virus and can be quantified in this testing process.
All SARS-CoV-2 viruses can be detected in wastewater, including the variants of concern that you may see in the news headlines. These variants are caused by small genetic changes (known by the term mutation) that naturally occur as the virus evolves and moves from person to person. These genetic changes can be identified by genome sequencing.
Please remember that the normal precautions like masking, physical distance, and hand washing all work to protect you against all forms of SARS-CoV-2.
How can I interpret a logarithmic scale?
You may be familiar with the Richter Scale, which is a logarithmic scale used to measure the magnitude of an earthquake. For example, you might not notice a great difference in an earthquake measuring a 2 and one measuring a 3, but an earthquake measuring a 6 is incredibly different, and is actually 10,000 times stronger than an earthquake measuring at a 2 on the Richter Scale.
How does this process work?
- Personnel set up specialized equipment that collects a representative sample from points in the sewer system over the course of a 24-hour period. Population data and wastewater flow rates are computed.
- Collected samples are brought to the University of Delaware (UD) Center for Environmental and Wastewater Epidemiological Research (CEWER) laboratory for further processing. The analysis includes steps to filter, concentrate, and test for the virus genetic material using the Polymerase Chain Reaction (PCR) procedure. PCR amplifies the signal so it can be detected and is the same type of analysis that is used to test for infection in humans.
- Through analysis of the PCR data, UD scientists look for the unique genetic signature of the SARS-CoV-2 virus in the samples.
- Quantification of the SARS-CoV-2 virus genetic material present in the water samples is made available to the public and shown on a graph with both upper and lower levels displayed. Correlations, connections, and forecasts can be made by connecting clinical information to the finding of varying levels of virus across the sewer shed.
Similar wastewater monitoring initiatives are occurring around the globe. To learn more about how this data is being used worldwide, visit
www.covid19wbec.org
.
How should I read this data?
The data depicted indicate the levels of virus (SARS-CoV-2) detected in different wastewater
samples. These data are given units of virus genetic material detected per a specific volume of water. This is an
estimate of the overall concentration of virus in the wastewater which can be impacted by the population
contributing to the watershed, the weather during the time of collection, and geography of the area. The SARS-
CoV-2 levels (viral copies/L) prior to 10/1/2021, for both Biobot and CEWER data, were generated using
quantitative PCR (qPCR) with a limit of quantification of 10,000 copies/L, set by CEWER. The data after
10/1/2021, were generated by CEWER using digital PCR (dPCR) with a limit of quantification of 250 copies/L. The
qPCR data were presented on the figure as normalized viral copies/L, which are the concentrations divided by a
factor of 100 to allow for visual consistency of the data to evaluate trends in the viral levels over time.
Why switch to a new methodology?
The new methodology (dPCR) was developed and implemented to provide increased sensitivity, decreased
limit of quantification, and align with methods used by the
CDC’s National Wastewater Surveillance System
. The NWSS was created to provide a network of wastewater surveillance throughout the United States. By
implementing this new method, we can compare data to neighboring institutions performing wastewater
surveillance. dPCR also allows for lower levels of SARS-CoV-2 to be detected and testing to be increased to
include more targets, such as influenza virus or norovirus.
Should I be concerned about contracting COVID-19 from the sewer system?
The testing performed here only detects the genetic material from the SARS-CoV-2 virus. While it is not likely that the virus detected is infectious or transmissible, this cannot be determined by this testing. The World Health Organization states that "there is no evidence to date that COVID-19 has been transmitted via sewage systems with or without wastewater treatment." Please note that the County’s sewer system is contained and inaccessible to the public, and all samples collected are prior to treatment and disinfection at the wastewater treatment plant.
Why does the dashboard no longer present prevalence rates?
As knowledge of the COVID-19 virus and how it is shed from the body has grown, it has been found that
current models predicting prevalence rate may not be as accurate as once thought. Instead, comparing
trends of viral concentration in wastewater compared to clinical cases provides helpful data that can be
used to help predict the magnitude, direction and extent of the pandemic.
Where is other COVID-19-related data for Delaware?
To see more COVID-19-related information for the State of Delaware, including clinical case estimates and vaccine information, go to the
Delaware Health and Human Services website at coronavirus.delaware.gov.
