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National Wastewater Surveillance System (NWSS)
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Wastewater data reporting may be reduced or delayed over the holiday season. Data will be updated as it becomes available.
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).
About CDC’s Wastewater Program (NWSS)
How Wastewater Monitoring Works
Wastewater Influenza A National Trends
Influenza A Wastewater Data
Influenza A Wastewater Monitoring in the U.S.
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Situational Summary
* 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.
What can wastewater data for influenza A virus tell us?
* If influenza (flu) A virus is increasing or high in an area’s wastewater, public health officials also look to other data sources, like clinical and agricultural data, to understand whether the virus might be coming from humans (such as seasonal influenza) or animals (such as from an outbreak of bird flu).
* Testing for influenza A virus in community wastewater can provide a signal that humans or animals may be infected with the virus.
* Influenza A viruses include multiple subtypes (e.g., viruses with H1, H3, or H5). These include subtypes that cause seasonal influenza in people each year and subtypes that can cause outbreaks among both animals and people, such as bird flu.
* Wastewater data do not identify whether detections or increases of influenza A virus are coming from humans, an animal product (like milk from an infected cow), or an animal (like a bird). Some sewer systems are more open to environmental input than others and may have animal inputs, and this can impact detections.
* Wastewater testing for an influenza A(H5) subtype is happening across the United States. See Wastewater Data for Avian Influenza A(H5) for more information.
2
Nationally, the wastewater viral activity level for influenza A is currently very low .
Wastewater data are updated every Friday with the previous week’s data, which allows for data to be reviewed for accuracy.
This chart shows national trends of wastewater viral activity levels of influenza A.
1 Year6 Months45 DaysAll Results
Skip Over Chart Container
No Data AvailableMinimalLowModerateHighVery High
Very LowLowModerateHighVery High06/01/2407/13/2408/24/2410/05/2411/16/2412/28/2402/08/2503/22/2505/03/25Week Ending
National
Data from the most recent two weeks may be incomplete due to delays in data reporting. These data sets are subject to change and are indicated by the gray shading.
Data last updated 2024-12-26
Data last updated 2025-05-08
Skip Data Table
Data Table
Data table showing data for the chart figure.
No Data
Week_Ending_Date Press command, modifier, or enter key to sort by Week_Ending_Date in ascending order National Press command, modifier, or enter key to sort by National in ascending order
05/03/25 1.37
04/26/25 1.49
04/19/25 1.91
04/12/25 2.42
04/05/25 2.41
03/29/25 2.85
03/22/25 4.16
03/15/25 5.16
03/08/25 8.68
03/01/25 11.90
02/22/25 13.88
02/15/25 18.64
02/08/25 21.74
02/01/25 21.40
01/25/25 18.90
01/18/25 13.05
01/11/25 11.48
01/04/25 11.76
12/28/24 8.19
12/21/24 5.66
12/14/24 3.80
12/07/24 2.36
11/30/24 1.67
11/23/24 1.65
11/16/24 1.53
11/09/24 1.37
11/02/24 1.22
10/26/24 1.14
10/19/24 1.20
10/12/24 1.15
10/05/24 1.32
09/28/24 1.30
09/21/24 1.16
09/14/24 1.18
09/07/24 1.24
08/31/24 1.28
08/24/24 1.26
08/17/24 1.23
08/10/24 1.36
08/03/24 1.26
07/27/24 1.37
07/20/24 1.43
07/13/24 1.35
07/06/24 1.28
06/29/24 1.44
06/22/24 1.35
06/15/24 1.54
06/08/24 1.67
06/01/24 1.76
05/25/24 1.77
05/18/24 2.10
05/11/24 2.40
05/04/24 2.28
Link to DatasetDownload Data (CSV)
Skipped data table.
About the Data
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:
About the Wastewater Viral Activity Level: The wastewater viral activity level indicates whether the amount of virus in the wastewater is very low, 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
* Up to 1.6 – Very Low
* 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).
Explore more Influenza A Wastewater Monitoring Data
Influenza A Current Wastewater Viral Activity Levels
Wastewater Data for H5
Wastewater Influenza A State and Territory Trends
Other Links
* CDC’s Wastewater (NWSS) Program
* How Wastewater Monitoring Works
* About Wastewater Data
* Mpox Wastewater Data
* Current Activity Levels
Last Reviewed: December 6, 2024
Source: Centers for Disease Control and Prevention
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