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How CDC is monitoring influenza data among people to better understand the current avian influenza A (H5N1) situation
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Updated April 24, 2024
Weekly Snapshot for Week Ending April 13, 2024
CDC influenza (flu) surveillance systems show no indicators of unusual influenza activity in people, including avian influenza A(H5N1).
This page provides information on how CDC systems that monitor national, state, and local level influenza data are being used during the current avian influenza A(H5N1) situation
Case Reporting
In 2024, one human case of influenza A(H5N1) virus infection has been reported by one state (Texas), following exposure to dairy cattle. A total of 2 human cases of A(H5N1) have been reported in the United States ever, with the first case occurring in 2022, following exposure to presumably infected poultry.
Clinical Laboratory Trends
CDC has not identified any unusual trends in reported clinical laboratory data at the national, state, or local levels.
Public Health Laboratory Monitoring
No novel influenza A positive test results, including for influenza A(H5N1) virus, were reported by public health laboratories for the week ending April 13, 2024.
Emergency Departments
CDC has not identified any unusual trends in emergency department visits associated with influenza or potentially related symptoms at the national, state, or local levels.
Monitoring for Novel Influenza A Virus Infections among People, including Influenza A(H5N1)
Rapid detection and reporting of human infections with novel influenza A viruses, including influenza A(H5N1), is important to facilitate prompt awareness and an effective public health response. For confirmed cases, the reporting jurisdiction completes a case report form, which is submitted to CDC. The information includes patient demographics, symptoms, the clinical course of illness, and exposure history. The reporting jurisdiction for influenza A(H5N1) cases reported in 2024 are summarized below.
Data presented through:04/13/2024; Data as of: 04/18/2024
Additional novel influenza case surveillance information for current and past seasons:
Surveillance Methods | FluView Interactive: Case Characteristics
Public Health Laboratory Reporting
Public health laboratories use CDC’s diagnostic tools to detect both seasonal influenza viruses and novel influenza A viruses including influenza A(H5N1). These diagnostic tools are used at more than 100 public health laboratories in all 50 U.S. states. The results of tests performed by these public health laboratories nationwide are summarized below.
Data presented through: 04/13/2024; Data as of: 04/18/2024
Additional virologic surveillance information for current and past seasons:
Surveillance Methods | FluView Interactive: National, Regional, and State Data or Age Data Systems Used to Monitor Influenza Activity
Influenza activity is monitored year-round using multiple systems. These systems are used for monitoring seasonal influenza and, because influenza viruses are constantly changing in small, and occasionally more significant ways, these systems are also useful for monitoring signals and trends from novel influenza virus infections. Some examples are provided below.
Monitoring for Changes in Tests Positive for Influenza in Clinical Settings
Approximately 300 clinical laboratories located throughout all 50 states, Puerto Rico, Guam, and the District of Columbia report the results of clinical testing for influenza through either the U.S. WHO Collaborating Laboratories System or the National Respiratory and Enteric Virus Surveillance System (NREVSS). The results of tests performed by clinical laboratories nationwide are summarized below. While these laboratories don’t test specifically for influenza A(H5N1) virus, by tracking the percentage of specimens tested that are positive for influenza A viruses, we can monitor for unusual increases in influenza activity that may be an early sign of spread of novel influenza A viruses, including H5N1.
Data presented through: 04/13/2024; Data as of: 04/18/2024
Additional clinical laboratory surveillance information for current and past seasons:
Surveillance Methods | FluView Interactive: National, Regional, and State Data
Monitoring for Changes in Emergency Department Visits for Influenza
The National Syndromic Surveillance Program (NSSP) collects, analyzes, and shares electronic data received from multiple health care settings, including emergency departments (ED). Data from NSSP on the weekly percentage of total emergency department visits associated with influenza-related diagnoses are summarized below. It’s important to note that these visits are among persons with any influenza diagnosis and are not specific to H5N1. However, by tracking all influenza diagnoses, as well as symptoms potentially related to influenza virus infections, among patients in EDs, the chance of detecting unusual levels of influenza is improved, including in jurisdictions where the virus has been identified in people or animals. StateUnited StatesAlabamaAlaskaArizonaArkansasCaliforniaColora doConnecticutDelawareDistrict of ColumbiaFloridaGeorgiaHawaiiIdahoIllinoisIndianaIo waKansasKentuckyLouisianaMaineMarylandMassachusett sMichiganMinnesotaMississippiMontanaNebraskaNevada New JerseyNew MexicoNew YorkNorth CarolinaNorth DakotaOhioOklahomaOregonPennsylvaniaRhode IslandSouth CarolinaTennesseeTexasUtahVermontVirginiaWashingto nWest VirginiaWisconsinWyoming CountyAll Counties included in this area
Weekly percent of total emergency department visits associated with influenza
Skip Over Chart Container
Percent of Emergency Department VisitsWeek Ending
Data presented through: 04/13/2024; Data as of: 04/17/2024
Dataset on data.cdc.gov | Link to Dataset Skip Data Table
Data Table Skipped data table.
Additional emergency department surveillance information for current and past seasons:
Surveillance Methods |Data.CDC.gov: NSSP Emergency Department Visit Trajectories
Explore Deeper
Weekly U.S. Influenza Surveillance Report
Novel A FluView Interactive
Respiratory Virus Data Channel Weekly Snapshot
https://www.cdc.gov/flu/avianflu/h5-monitoring.html
Español | Other Languages
Updated April 24, 2024
Weekly Snapshot for Week Ending April 13, 2024
CDC influenza (flu) surveillance systems show no indicators of unusual influenza activity in people, including avian influenza A(H5N1).
This page provides information on how CDC systems that monitor national, state, and local level influenza data are being used 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.
Case Reporting
In 2024, one human case of influenza A(H5N1) virus infection has been reported by one state (Texas), following exposure to dairy cattle. A total of 2 human cases of A(H5N1) have been reported in the United States ever, with the first case occurring in 2022, following exposure to presumably infected poultry.
Clinical Laboratory Trends
CDC has not identified any unusual trends in reported clinical laboratory data at the national, state, or local levels.
Public Health Laboratory Monitoring
No novel influenza A positive test results, including for influenza A(H5N1) virus, were reported by public health laboratories for the week ending April 13, 2024.
Emergency Departments
CDC has not identified any unusual trends in emergency department visits associated with influenza or potentially related symptoms at the national, state, or local levels.
Monitoring for Novel Influenza A Virus Infections among People, including Influenza A(H5N1)
Rapid detection and reporting of human infections with novel influenza A viruses, including influenza A(H5N1), is important to facilitate prompt awareness and an effective public health response. For confirmed cases, the reporting jurisdiction completes a case report form, which is submitted to CDC. The information includes patient demographics, symptoms, the clinical course of illness, and exposure history. The reporting jurisdiction for influenza A(H5N1) cases reported in 2024 are summarized below.
Data presented through:04/13/2024; Data as of: 04/18/2024
Additional novel influenza case surveillance information for current and past seasons:
Surveillance Methods | FluView Interactive: Case Characteristics
Public Health Laboratory Reporting
Public health laboratories use CDC’s diagnostic tools to detect both seasonal influenza viruses and novel influenza A viruses including influenza A(H5N1). These diagnostic tools are used at more than 100 public health laboratories in all 50 U.S. states. The results of tests performed by these public health laboratories nationwide are summarized below.
Data presented through: 04/13/2024; Data as of: 04/18/2024
Additional virologic surveillance information for current and past seasons:
Surveillance Methods | FluView Interactive: National, Regional, and State Data or Age Data Systems Used to Monitor Influenza Activity
Influenza activity is monitored year-round using multiple systems. These systems are used for monitoring seasonal influenza and, because influenza viruses are constantly changing in small, and occasionally more significant ways, these systems are also useful for monitoring signals and trends from novel influenza virus infections. Some examples are provided below.
Monitoring for Changes in Tests Positive for Influenza in Clinical Settings
Approximately 300 clinical laboratories located throughout all 50 states, Puerto Rico, Guam, and the District of Columbia report the results of clinical testing for influenza through either the U.S. WHO Collaborating Laboratories System or the National Respiratory and Enteric Virus Surveillance System (NREVSS). The results of tests performed by clinical laboratories nationwide are summarized below. While these laboratories don’t test specifically for influenza A(H5N1) virus, by tracking the percentage of specimens tested that are positive for influenza A viruses, we can monitor for unusual increases in influenza activity that may be an early sign of spread of novel influenza A viruses, including H5N1.
Data presented through: 04/13/2024; Data as of: 04/18/2024
Additional clinical laboratory surveillance information for current and past seasons:
Surveillance Methods | FluView Interactive: National, Regional, and State Data
Monitoring for Changes in Emergency Department Visits for Influenza
The National Syndromic Surveillance Program (NSSP) collects, analyzes, and shares electronic data received from multiple health care settings, including emergency departments (ED). Data from NSSP on the weekly percentage of total emergency department visits associated with influenza-related diagnoses are summarized below. It’s important to note that these visits are among persons with any influenza diagnosis and are not specific to H5N1. However, by tracking all influenza diagnoses, as well as symptoms potentially related to influenza virus infections, among patients in EDs, the chance of detecting unusual levels of influenza is improved, including in jurisdictions where the virus has been identified in people or animals. StateUnited StatesAlabamaAlaskaArizonaArkansasCaliforniaColora doConnecticutDelawareDistrict of ColumbiaFloridaGeorgiaHawaiiIdahoIllinoisIndianaIo waKansasKentuckyLouisianaMaineMarylandMassachusett sMichiganMinnesotaMississippiMontanaNebraskaNevada New JerseyNew MexicoNew YorkNorth CarolinaNorth DakotaOhioOklahomaOregonPennsylvaniaRhode IslandSouth CarolinaTennesseeTexasUtahVermontVirginiaWashingto nWest VirginiaWisconsinWyoming CountyAll Counties included in this area
Weekly percent of total emergency department visits associated with influenza
Skip Over Chart Container
Percent of Emergency Department VisitsWeek Ending
Data presented through: 04/13/2024; Data as of: 04/17/2024
Dataset on data.cdc.gov | Link to Dataset Skip Data Table
Data Table Skipped data table.
Additional emergency department surveillance information for current and past seasons:
Surveillance Methods |Data.CDC.gov: NSSP Emergency Department Visit Trajectories
Explore Deeper
Weekly U.S. Influenza Surveillance Report
Novel A FluView Interactive
Respiratory Virus Data Channel Weekly Snapshot
https://www.cdc.gov/flu/avianflu/h5-monitoring.html