Description

Introduction

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The Georgia Department of Public Health (DPH) is participating in the Centers for Disease Control (CDC) Health and Human Services (HHS) National Wastewater Surveillance System (NWSS). Starting in April 2022, DPH began conducting weekly wastewater sampling to better understand COVID-19 trends in Georgia. When used alongside case-based data, wastewater surveillance can provide insight into community level transmission.

The Georgia NWSS Program is a collaboration between the Georgia Department of Public Health, Georgia Public Health Laboratory (GPHL), local public health departments, Emory University Rollins School of Public Health & University of Georgia wastewater surveillance researchers, and wastewater facilities.

Methods

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Wastewater sample collection

Wastewater treatment facility (WWTF) partners generally collect two raw wastewater samples per week. This raw wastewater includes human feces, other things such as stormwater runoff, and anything that may end up in the sewer system after washing our hands, brushing our teeth, or using the bathroom.

Extraction & quantification of genetic material

Two gene targets, N1 and N2, are used in answering two important questions:

  1. Is there evidence of SARS-CoV-2 (the virus that causes COVID-19) genetic material within the wastewater sample?

    This helps us learn whether there is at least one individual with COVID-19 infection in the community.

  2. How much viral genetic material is present within the sample?

    This helps us understand the level of community transmission. This also allows public health to monitor changes in trends over time.

Data Normalization

Normalization is a statistical method that reduces variability across different facilities. These include factors such as flow rate, number of gallons a facility treats per day, and the number of persons served by the facility. This both improves the accuracy of the data by reducing excess variation and allows us to directly compare SARS-CoV-2 concentrations/levels at different facilities over time.

The two main methods of normalization are: (1) by flow rate and population or (2) by PMMoV concentration. All normalized data within this report has been normalized by flow rate and population size (estimated number of persons served by the facility).

Trend Estimation

Smoothing techniques are used to fit a trendline to the data and produce final concentration estimates. These estimates may change as new data is entered.

Additional Resources

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Below are additional resources from CDC and partners regarding wastewater surveillance both in Georgia and the U.S.

Summary Report

Data updated as of March 22, 2023

Wastewater Surveillance of COVID-19 over Time

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Georgia is currently collecting wastewater data from 12 sites and is one of 46 states contributing to CDC NWSS.

When interpreting wastewater data, it is best to assess trends over time and compare those to case-based data and in the context of community level transmission. For example, if SARS-CoV-2 concentrations are increasing, this means that the number of individuals shedding SARS-CoV-2 in their stool is increasing. This could be due to a true increase in individuals with COVID-19 or the movement of ‘new’ individuals in a population e.g., a large sporting event, work conference, etc.

For a more detailed summary of case trends in your County, please see the DPH COVID-19 Status Report page: https://dph.georgia.gov/covid-19-status-report.

SARS-CoV-2 Concentration Data Over Time

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Normalized Concentration Versus Cases