What to Know About Wastewater Surveillance for COVID-19

Medically Reviewed by Dan Brennan, MD on January 02, 2023
4 min read

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

Data from the NWSS is meant to help along with other COVID-19 trackers. It is not the only form of COVID-19 surveillance. It can provide more information to gain a useful community sample, data for areas that don’t have timely COVID-19 testing, or statistics on various communities within a county.

Wastewater refers to the water from buildings or homes that could 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 shed 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 don’t have any symptoms of COVID-19. The NWSS can then locate viral RNA from any current cases in your community in the wastewater from your area.

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

Your community’s health departments will 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.

The NWSS uses the DCIPHER tool to study the data. It’ll send back the results to your community’s health department. Through this, health experts in your area will be able to prepare ahead of time if there’s a surge in COVID-19 cases.

You can look at data from your community through the CDC’s COVID Data Tracker.

The NWSS can provide information that other COVID-19 surveillance tools may miss. It can also improve upon data that’s already collected. Data from wastewater surveillance can help:

  • Measure if COVID-19 infections are going up or down in your community.
  • Provide data on COVID-19 cases regardless of an area’s level of access to health care or COVID-19 testing (unlike other forms of COVID-19 surveillance).
  • Serve various types of communities, since 80% of homes in the United States connect to public wastewater collection systems.
  • Detect COVID-19 variants like Omicron.
  • Identify the COVID-19 virus 1 to 2 weeks earlier than it takes to receive results from clinical samples 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 therapeutics for the virus).

But the NWSS does have some limits:

  • Higher amounts of the COVID-19 virus in wastewater predict more cases of COVID-19 in an area. But wastewater testing can’t yet accurately find the number of people infected with COVID-19 in a community.
  • Community wastewater surveillance done at a treatment plant won’t include households that use a septic system.
  • They also won’t be able to collect data from decentralized systems, like prisons, hospitals, or universities that treat their waste.
  • The 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 surveillance sites. For example, some plants treat their wastewater before it even gets to the actual plant.

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

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

  • Waste could flow out of or into the damaged systems. As wastewater flows through low resource waste systems, some could spill into the environment. Similarly, polluted water could flow into the system.
  • If wastewater flows into open surface waters, canals, or drains, it could mix with other water in the natural world. This could impact the decay of the COVID-19 virus’s RNA.
  • Because of the two factors above, it’s hard to tell how long human waste has been in low-resource waste systems. This could impact a surveillance system’s ability to accurately measure COVID-19 cases.

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