At a glance
Overview
H5N1 Bird Flu Surveillance in U.S.
On July 7, 2025, CDC streamlined H5N1 bird flu updates with routine influenza data updates and updated reporting cadences to reflect the current public health situation. As such, several changes were made to this page:
- Data on the number of people monitored and tested for bird flu, as well as animal and epidemiologically linked human cases are reported monthly.
- Data that are reported in CDC's FluView, National Wastewater Surveillance System (NWSS), and The National Syndromic Surveillance Program (NSSP) will not be updated here but can be found on those respective webpages.
CDC uses multiple systems to monitor national, state, and local level influenza data during the current avian influenza A(H5N1) situation.
- Influenza virus and illness activity are monitored year-round through a collaborative effort between CDC and many partners, including state, local, and territorial health departments; public health and clinical laboratories; clinics; and emergency departments.
- Human cases of novel influenza, which are human infections with non-human influenza A viruses that are different from currently spreading seasonal human influenza viruses, are nationally notifiable. Every identified case is investigated and reported to CDC.
- CDC is actively looking at multiple flu indicators during the current situation to monitor for influenza A(H5N1) viruses, including looking for spread of the virus to, or among people, in jurisdictions where the virus has been identified in people or animals. More information is available: FluView.
Main Findings from Surveillance Systems
CDC has multiple surveillance systems that are used year-round to monitor key flu indicators. These data are reviewed comprehensively each week. Taken together, through June 2025, these systems did not show indicators of unusual flu activity in people, including avian influenza A(H5N1) viruses.
Case Reporting
For the latest case counts, please visit the H5 Bird Flu: Current Situation page.
Public Health Laboratory Monitoring
For more information on Public Health Laboratory testing visit FluView
Clinical Laboratory Trends
For more information on Clinical Laboratory trends visit FluView
Emergency Departments
For data on emergency department visits visit data.cdc.gov
Wastewater Surveillance
For more information on wastewater surveillance visit CDC’s National Wastewater Surveillance System (NWSS)
Monitoring of Persons Exposed to Infected Animals*
Note: Monitoring data of persons exposed to infected animals will be updated on the first Friday of every month.
February 2022 – May 2025
CDC and state and local health departments monitor people exposed to infected birds, poultry, dairy cows or other animals for 10 days after exposure. Between February 2022 and May 2025, there have been
- At least 27,900 people monitored and
- At least 1,180 people tested for novel influenza A
Current HPAI Outbreak (March 2024-Present)
CDC and state and local health departments monitor people exposed to infected birds, poultry, dairy cows and other animals for 10 days after exposure. Between March 24, 2024, and May 31, 2025, there have been
- At least 18,600 people monitored
- At least 9,600 with exposures to dairy cows
- At least 9,000 with exposures to birds and other animals including poultry (non-dairy cow source)
- At least 880 persons tested for novel influenza A
- At least 218 with exposures to dairy cows
- At least 670 with exposures to birds and other animals including poultry (non-dairy cow source)
*CDC numbers are based on weekly state aggregate reports since 2022. CDC defers to states for updated information on people being monitored and tested. March 24, 2024, was the date of the first reported dairy cow infections in the United States.
Monitoring for Novel Influenza A virus infections among people, including Influenza A(H5)
Note: Animal and epidemiologically linked human cases will be updated on the first Friday of every month.
Influenza H5 virus infections in humans exposed to affected animals by state
Data presented through: 06/28/2025; Data as of: 07/1/2025
Influenza A H5 affected dairy herds and epidemiologically linked human cases
Data presented through: 06/28/2025; Data as of: 07/1/2025
Influenza A H5 affected commercial poultry flocks and epidemiologically linked human cases
Influenza A H5 affected backyard flocks and epidemiologically linked human cases
Data presented through: 06/28/2025; Data as of: 07/1/2025
Wastewater Data for Avian Influenza A(H5)
Wastewater surveillance may complement other existing human influenza surveillance systems to monitor influenza. Data on wastewater testing for influenza A viruses can be found through CDC's National Wastewater Surveillance System (NWSS).