What you need to know about COVID-19 wastewater monitoring
What you need to know about COVID-19 wastewater monitoring

What you need to know about COVID-19 wastewater monitoring

The CDC launched the National Wastewater Surveillance System (NWSS) in September 2020. This tool allows experts to detect the virus that causes COVID-19 in wastewater or wastewater samples from across the country. NWSS helps health departments act quickly if they notice an increase in cases from wastewater samples. This system can protect your community from the spread of COVID-19 and any new variants.

Data from NWSS is intended to assist with other COVID-19 trackers. It should not be the only form of COVID-19 monitoring. It can provide more information to get a useful community sample, data for areas that do not have timely COVID-19 testing, or statistics on different communities in a county.

How does the national wastewater monitoring system identify an outbreak of COVID-19?

Wastewater refers to the water from buildings or homes that may contain human waste. This includes water from toilets, sinks and showers. Rainwater and water from industrial use could also be wastewater.

If you have COVID-19, your body will secrete viral RNA from the virus into your stool. Viral RNA, which is genetic material from the virus, will be present in human waste even if you have no symptoms of COVID-19. NWSS can then locate viral RNA from all current cases in your community in the wastewater from your area.

How does wastewater monitoring work?

Wastewater flows into a treatment plant from a specific sewer system. These are wastewater collection systems for different areas of society. From here, experts collect and send samples of wastewater to environmental or public health laboratories. They will test the samples for the COVID-19 virus at these sites.

Your community’s health departments send data from the tests to the CDC. They use the online NWSS Data Collection and Integration for Public Health Event Response (DCIPHER) portal to do this.

NWSS uses the DCIPHER tool to study the data. It sends the results back to your community’s health department. Through this, health experts in your area will be able to prepare in advance if there is an increase in COVID-19 cases.

You can view data from your community through CDC’s COVID Data Tracker.

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What are the benefits and limitations of the national wastewater monitoring system?

NWSS may provide information that other COVID-19 monitoring tools may miss. It can also enhance data already collected. Data from wastewater monitoring can help:

  • Targets for COVID-19 infections increase or decrease in your community.
  • Provide data on COVID-19 cases regardless of an area’s access level for health care or COVID-19 testing (as opposed to other forms of COVID-19 monitoring).
  • Serve different types of communities as 80% of homes in the United States connect to public wastewater collection systems.
  • Discover COVID-19 variants like Omicron.
  • Identify the COVID-19 virus 1 to 2 weeks earlier than it takes to receive results from clinical trials from the same area.
  • Monitor variants over time and learn more about the evolution of the COVID-19 virus. (This can help measure the success of vaccines, diagnostics and therapies for the virus).

But NWSS has some limitations:

  • Larger amounts of the COVID-19 virus in wastewater predict several cases of COVID-19 in an area. But sewage tests can not yet accurately find the number of people infected with COVID-19 in a community.
  • Community waste water monitoring carried out at a treatment plant does not cover households using a septic system.
  • They will also not be able to collect data from decentralized systems, such as prisons, hospitals or universities that treat their waste.
  • NWSS may not be able to detect anything if an area has a low percentage of people with COVID-19. Experts need more information to understand how to test for low levels of infection.
  • Not all wastewater treatment plants are useful for monitoring sites. For example, some plants purify their wastewater before it even reaches the actual plant.

Wastewater monitoring also faces some barriers in areas with low-resource waste systems. These areas include systems that have dilapidated structures. In these regions, environmental factors can also affect the quality of the wastewater (which may make it less accurate to test for the virus that causes COVID-19).

In areas with these systems, NWSS may not be as useful because:

  • Waste can flow out of or into the damaged systems. As wastewater flows through low-resource waste systems, something can spill into the environment. Similarly, contaminated water can flow into the system.
  • If wastewater flows into open surface water, canals or drains, it can mix with other water in the natural world. This may affect the decay of the RNA of the COVID-19 virus.
  • Due to the two factors above, it is difficult to say how long human waste has been in low-resource waste systems. This may affect the ability of a monitoring system to accurately measure COVID-19 cases.

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Can wastewater collection with covid-19 virus lead to more cases?

No. There is viral RNA from COVID-19 in human waste from people who have the virus. However, the CDC states that there is no data to suggest that anyone has become ill with COVID-19 after close contact with treated or untreated wastewater.



CDC: “Wastewater Monitoring”, “Low-Resource Waste Systems.”

County of Santa Clara: “SARS-CoV-2 Wastewater Monitoring Data.”

Syracuse University News: “Understanding COVID-19 transmissions in our society through wastewater monitoring.”

FDA: “Sewage Monitoring for SARS-CoV-2 Variants.”

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