In 2020, the U.S. Centers for Disease Control and Prevention (CDC) partnered with local health departments and launched the National Wastewater Surveillance System (NWSS) to track SARS-CoV-2 virus levels in wastewater around the country. The goal was to help health officials quickly implement policies to mitigate the spread of the virus.1
The CDC recently confirmed that there has been an increase in the level of the SARS-CoV-2 virus found in some wastewater samples across the United States. However, even though more than one-third of the water samples showed an uptick in levels of SARS-CoV-2 from Mar. 1 to Mar. 10, 2022, reportedly COVID cases and hospitalizations across the country have been declining and remain low.2
Amy Kirby, PhD, MPH, the head of the CDC’s wastewater monitoring program said:
While wastewater levels are generally very low across the board, we are seeing an uptick of sites reporting an increase. These bumps may simply reflect minor increases from very low levels to still low levels. Some communities though may be starting to see an increase in Covid-19 infections, as prevention strategies in many states have changed in recent weeks.”3
Dr. Kirby added:
It’s too early to know if this current trend will continue or whether we’ll see a corresponding increase in reported cases across the country.4
Wastewater Surveillance Used as Tool to Predict Spread of SARS-CoV-2 in Communities
Data from wastewater testing is used to drive public health policies by providing information about the prevalence of SARS-CoV-2 in a particular community. The CDC states that people infected with SARS-CoV-2 can shed the virus in their feces, even if they don’t have symptoms. The virus can then be detected in wastewater, which allows wastewater surveillance to capture presence of SARS-CoV-2 shed by people with and without symptoms.5
According to Mike Chiazza, operations supervisor of water pollution control with the Wheeling Public Works Department in West Virginia:
In Athens (West Virginia), they’re having an outbreak that they think was from one event, and it can pick up stuff like that. The good thing about this is you don’t actually have to have someone go out and get the test, because everyone’s using their toilets.6
Chiazza said, “You shed the virus in your waste before you actually come down with symptoms,”7 thus making it possible to identify a future outbreak.
The CDC says that, unlike other types of SARS-CoV-2 surveillance, wastewater surveillance does not depend on whether people having access to health care facilities or whether sick people seek health services or whether SARS-CoV-2 testing is readily available. Since 80 percent of American households are served by municipal wastewater collection systems, wastewater surveillance can be implemented in many communities.8
The CDC has stated that, while the SARS-CoV-2 virus can shed in feces, there is no current information about people getting infected with the SARS-CoV-2 virus when directly exposed to treated or untreated wastewater.9
Recent Wastewater Surveillance of SARS-CoV-2 Shows Contradictory Data
The CDC has said that wastewater surveillance for the virus that causes COVID-19 is a developing field and has many limitations.10 Contradictory data from wastewater surveillance has emerged.
For example, several sites in the Chicago area reported SARS-CoV-2 levels had dropped by up to 99 percent from Feb. 27 to Mar. 13, 2022, but one site showed an increase of least 1,000 percent.11 In Miami-Dade County, one sample site showed a decline in the amount of SARS-CoV-2 virus found in wastewater. However, two other sites in the same county showed an increase in virus levels.
Although there may be several reasons for conflicting information, so far CDC officials have not provided explanations for why there are inconsistencies in the data.12
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Click here to view References:
1 U.S. Centers for Disease Control and Prevention. National Wastewater Surveillance System (NWSS). Feb. 4, 2022.
2 Edwards E, Siemaszko C. CDC confirms uptick in Covid virus found in wastewater. NBC News Mar. 15, 2022.
3 Armstrong D, Tartar A. U.S. Sewer Data Warns of a New Bump in Covid Cases After Lull. Bloomberg Mar. 14, 2022.
5 CDC. National Wastewater Surveillance System (NWSS). Feb. 4, 2022.
6 Olson A. Testing Sewage Can Foretell a COVID-19 Outbreak. The Intelligencer Mar. 14, 2022.
8 CDC. National Wastewater Surveillance System (NWSS). Feb. 4, 2022.
11 Smith Z. Coronavirus Rates Jump At Some Wastewater Testing Sites—Even As Case Counts Decline. Forbes Mar. 14, 2022.
12 Armstrong D, Tartar A. U.S. Sewer Data Warns of a New Bump in Covid Cases After Lull. Bloomberg Mar. 14, 2022.