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Wastewater surveillance may complement other existing human surveillance systems to monitor influenza. Wastewater data cannot determine the source of influenza A viruses. Detections could come from a human or from an animal (like a bird) or an animal product (like milk from an infected cow).
Wastewater Influenza A National Trends
Influenza A Wastewater Monitoring in the U.S.
- The ongoing avian influenza A (H5) (bird flu) outbreak in U.S dairy cows and poultry may be contributing to the moderate and high influenza (flu) A virus wastewater levels in some jurisdictions, based on reviewing multiple data sources. The risk to the public of avian influenza A (H5) is currently low.
- Wastewater data for influenza A virus should be considered in combination with clinical sources of influenza A data.
- Influenza A viruses include subtypes like avian influenza A(H5) virus and A(H1N1). Wastewater testing for overall influenza A virus cannot tell us what subtypes are present. Wastewater testing cannot tell us if the source of the influenza A virus is from humans, animals, or animal products.
- Wastewater testing for influenza virus subtypes, including an H5 subtype, is underway across the United States. See Wastewater Data for Avian Influenza A(H5) for more information.
- CDC and public health partners continue to investigate whether changing levels of influenza A virus in wastewater are related to seasonal influenza, the avian influenza A (H5) outbreak in animals, or both.
This chart shows national trends of wastewater viral activity levels of influenza A.
Wastewater monitoring can detect viruses spreading from one person to another within a community earlier than clinical testing and before people who are sick go to their doctor or hospital. It can also detect infections without symptoms. If you see increased wastewater viral activity levels, it might indicate that there is a higher risk of infection. See how to protect yourself from respiratory viruses.
About the Wastewater Viral Activity Level: The wastewater viral activity level indicates whether the amount of virus in the wastewater is minimal, low, moderate, high, or very high. The wastewater viral activity levels may indicate the risk of infection in an area. The wastewater viral activity levels are categorized as follows:
- Up to 1.6 – Minimal
- Greater than 1.6 and up to 4.5 – Low
- Greater than 4.5 and up to 12.2 – Moderate
- Greater than 12.2 and up to 20.1 – High
- Greater than 20.1 – Very High
National data represent the median values across all wastewater treatment plants. To learn more on how the wastewater viral activity level is calculated, see Data Methods.
Data Limitations: Wastewater data cannot determine the source of influenza A viruses. Detections could come from a human or from an animal (like a bird) or an animal product (like milk from an infected cow).
