About Wastewater Data

Wastewater monitoring data are most useful when used with other data, such as hospital visits or clinical testing data. Wastewater data are primarily used in four ways:

• Monitoring for the presence of infections in a community, regardless of whether the infections cause severe illness, mild illness, or no symptoms at all. By acting as an early warning system, wastewater monitoring can detect small changes early and take quick action to prevent further infections.
• Tracking trends in infection in a community whose sewage flows into a wastewater treatment plant (known as a sewershed).
• Tracking infection trends within a state, region, and nationally.
• Monitoring variants of a virus that are causing infections in a community.

More data over time can give health departments better, more reliable insights into trends that are happening in a community, state, region, and the nation. Public health officials watch for sustained increasing levels of viruses and bacteria in wastewater and use these data to inform public health decisions. State and local health officials track a variety of data and put this information together to understand the local situation and decide how to best respond.

Wastewater monitoring can detect viruses spreading from one person to another within a community earlier than clinical testing and before they go to their doctor or hospital. It can also detect infections without symptoms. If you see increased Wastewater Viral Activity Levels of SARS-CoV-2, it might indicate that there is a higher risk of infection. See how to protect yourself from respiratory viruses like COVID-19 and Flu.

Wastewater data are updated every Friday with the previous week’s data, which allows for data to be reviewed for accuracy. Analyzed data are available for download from data.cdc.gov. The full NWSS dataset, including raw data, is available by submitting a data request to NWSS@cdc.gov.

NWSS recommends wastewater testing twice per week at each site across the United States and in territories and select tribal nations. For the latest number of sites reporting data, see About CDC’s Wastewater (NWSS) Program.

Wastewater samples contain a mix of DNA and RNA from bacteria, viruses, animals, humans, and other living things. CDC takes multiple steps as part of its wastewater surveillance program to ensure that the privacy of individuals contributing to wastewater is protected. CDC's wastewater program monitors infectious diseases and does not track or assess human genomic data.

Here are examples of how CDC’s wastewater program is protecting individuals’ data:

• Community-level data: Wastewater is collected from a combined, community-level sample not from an individual person or household.
• Population size: Sampling covers a large enough population that wastewater testing results for infectious diseases won’t be associated with an individual person.
• Public data display policies: CDC will not publicly display any wastewater detections that could be used in combination with clinical diagnostic testing data to identify an individual. Locations for wastewater treatment plants are approximated. Locations may be also adjusted to allow sites within close proximity to be more easily distinguished on a map. In addition, CDC does not publicly display data that meet any of the following criteria:
  • Data from sewersheds that serve fewer than 3,000 people
  • Data from facility or institution-specific sampling locations
  • Data from tribal communities
  • Data from sewersheds with known data quality issues.
• Data privacy technology: CDC uses the publicly available NCBI Human Read Removal Tool to ensure that any potential remaining human DNA is removed. CDC receives most sequencing data via NCBI, which removes any human DNA sequences before the data is sent to CDC
• Scientific limitations: Multiple factors protect the privacy of individuals when wastewater is used for public health.
  • Wastewater contains fragments of genetic material from thousands of people, making it unlikely that any single individual could be identified.
  • Every person has their own unique genome, or DNA "fingerprint." To identify an individual, one would need to match the DNA fragments from wastewater to their DNA fingerprint. Although there is a small, theoretical chance this could happen, it is highly unlikely. CDC does not have individuals' DNA fingerprints and therefore cannot match DNA fragments found in wastewater with individuals.
• Preparing for the future:
  • CDC will continue to preserve individual privacy and prioritize data stewardship as technology evolves, including changing policies if technologies emerge that enable individual identification using wastewater data.
  • CDC will adhere to ethical standards in wastewater science [PDF – 33 pages] to ensure individual privacy is protected and public health is enhanced. CDC will work with participating communities to understand ongoing priorities and concerns.

Data collected in CDC’s National Wastewater Surveillance System may over-represent certain populations within a state or territory. For example, most jurisdictions report data from municipal sewer system samples and may have limited inclusion of populations that rely on other non-sewered sanitation systems (e.g. septic tanks). They may also over-represent urban and suburban populations because of wastewater utility locations and the associated sewershed. As a result, these data may not accurately depict the full picture of viral activity for the entire state or territory.

The data presented are preliminary and may change as more data are received. Differences in the data presented by CDC and state health departments likely represent differing levels of data reporting; data presented by the state are likely the more complete ones. Additionally, there may be differences in data visualization approaches that impact how data are displayed.

Specific wastewater data limitations for each pathogen will be available in the data footnotes or About the Data sections:

• SARS-COV-2
• Influenza A
  • Avian Influenza A (H5)
• RSV
• Mpox