The Centers for Disease Control and Prevention and the U.S. Department of Health and Human Services, in collaboration with agencies throughout the federal government, are initiating the National Wastewater Surveillance System in response to the COVID-19 pandemic.

The data generated by NWSS aims to help public health officials better understand the extent of COVID-19 infections in communities.

CDC is currently developing a portal for state, tribal, local and territorial health departments to submit wastewater testing data into a national database for use in summarizing and interpreting data for public health action. Participation in a national database will ensure data comparability across jurisdictions.

Data from wastewater testing is not meant to replace existing COVID-19 surveillance systems, but is meant to complement them by providing an efficient pooled community sample; data for communities where timely COVID-19 clinical testing is underutilized or unavailable; and data at the sub-county level.

What are the advantages of wastewater infectious disease surveillance?

Sewage testing has been successfully used as a method for early detection of other diseases, such as polio. SARS-CoV-2 can be shed in the feces of individuals with symptomatic or asymptomatic infection; therefore, wastewater surveillance can capture data on both types of infection.

Nearly 80% of United States households are served by municipal sewage collection systems.

Quantitative SARS-CoV-2 measurements in untreated sewage can provide information on changes in total COVID-19 in the sewershed.

Depending on the frequency of testing, sewage surveillance can be a leading indicator of changes in COVID-19 burden in a community.

SARS-CoV-2 RNA detection in sewage serves as a COVID-19 indicator that is independent of healthcare-seeking behaviors and access to clinical testing.

Is wastewater surveillance right for my community?

Wastewater surveillance for RNA of the virus that causes COVID-19 is a developing field. Health departments setting up a sewage-based infectious disease surveillance system should consider the following to generate data that is useful for public health response, according to the CDC:

• Sewage testing over time can provide trend data that can complement other surveillance data that informs public health decision making. However, at this time, it is not possible to reliably and accurately predict the number of infected individuals in a community based on sewage testing.

• Community-level wastewater surveillance at a treatment plant will not capture homes on a septic-based system.

• Community-level wastewater surveillance at a wastewater treatment plant also will not capture communities or facilities served by decentralized systems, such as prisons, universities or hospitals that treat their waste.

• Low levels of infection in a community may not be captured by sewage surveillance. The lower limits of detection (i.e., the smallest number of people shedding the virus in stool that can still be detected by current testing methods) for sewage surveillance are not yet well understood. More data on fecal shedding by infected individuals over the course of disease are needed to better understand the limits of detection.

• All wastewater treatment plants may not be appropriate as sites for surveillance given their operations logistics (including if sewage is pre-treated before it reaches the plant.)

How do I become engaged in NWSS?

Using wastewater surveillance for public health action requires a multidisciplinary approach, according to the CDC. Communities interested in conducting wastewater surveillance for COVID-19 should identify the necessary local partners for sample collection, testing and public health action.

Local partners should include state, local, tribal and territorial health departments; COVID-19 epidemiologists; environmental health epidemiologists; laboratory scientists; wastewater treatment plants and workers; and testing laboratories. The CDC is not currently accepting sewage samples for testing.

National Wastewater Surveillance System (NWSS) is currently ramping-up efforts through partnerships with state, local, tribal and territorial health departments. Additional information, including sampling, testing and interpretation guidance, minimum reporting requirements, and instructions for reporting through the data portal will be updated on this page as they become available.

For a further overview of the topic, a recording of a CDC COVID-19 Sewage Surveillance webinar presented to the Council of State and Territorial Epidemiologists on July 8, 2020, is available here.