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Avian Influenza

CDC Current Bird Flu Situational Summary

Highly pathogenic avian influenza (HPAI) A(H5) viruses have been detected in U.S. wild aquatic birds, commercial poultry and backyard or hobbyist flocks beginning in January 2022. These are the first detections of HPAI A(H5) viruses in the U.S. since 2016. Preliminary genetic sequencing and RT-PCR testing on some virus specimens shows these viruses are HPAI A(H5N1) viruses from clade 2.3.4.4.

NOTE: On March 29, 2024 the CDC announced new interim recommendations for prevention, monitoring, and public health investigations of highly pathogenic avian influenza A(H5N1) virus in animals. Updates to this page are forthcoming.

Overview of H5N1 Detections in the United States
Last Updated: March 18, 2025
Dairy Cattle: On-going multi-state outbreak Human Cases: 70 cases in the U.S.
Wild Birds:  Widespread Human Deaths: 1 death in the U.S.
Poultry Flocks: Sporadic outbreaks Person-to-person spread: None
Mammals:  Sporadic infections Current public health risk: Low
Current Risk Assessment

CDC assessed the risk posed by highly pathogenic avian influenza (HPAI) A(H5N1) viruses to the United States.

The current risk to the general U.S. population is low. The risk to populations exposed to potentially infected animals, including through contaminated surfaces or fluids, is currently assessed as moderate to high. CDC has moderate confidence in this assessment.

Note: The likelihood of exposure is higher among people consuming raw (unpasteurized) milk from infected animals, although the chance of people acquiring H5N1 virus infection from consuming raw milk is not clear at this time.

 

These data will be updated daily, Monday through Friday, after 4 p.m. to reflect any new data.

Cumulative data on wild birds have been collected since January 20, 2022. Cumulative data on poultry have been collected since February 8, 2022. Cumulative data on humans in the U.S. have been collected since April 28, 2022. Cumulative data on dairy cattle have been collected since March 25, 2024.

Detections in Animals
  • 12,581 wild birds detected as of 3/18/2025 | Full Report
  • 51 jurisdictions with bird flu in wild birds
  • 168,234,214 poultry affected as of 3/20/2025 | Full Report
  • 51 jurisdictions with outbreaks in poultry
  • 989 dairy herds affected as of 3/18/2025 | Full Report
  • 17 states with outbreaks in dairy cows
Latest CDC Bird Flu News

March 19 CDC A(H5N1) Bird Flu Response Update March 19, 2025

February 28 Risk to People in the United States from Highly Pathogen Avian Influenza A(H5N1) Viruses

February 26 CDC A(H5N1) Bird Flu Response Update February 26, 2025

January 15  H5 Bird Flu Response: Focus Areas for Ongoing Public Health Risk Assessment 

January 10  Interim Guidance for Employers to Reduce Exposure to Avian Influenza A Viruses (Such as H5N1) for People Working with Animals

January 6  Information for Employers Providing Personal Protective Equipment to Reduce Exposure to Avian Influenza A Viruses 

January 6  Information for Workers Exposed to H5N1 Bird Flu

December 26  Genetic Sequences of Highly Pathogenic Avian Influenza A(H5N1) Viruses Identified in a Person in Louisiana

CDC A(H5N1) Bird Flu Response Update

CDC A(H5N1) Bird Flu Response Update

Last Updated: March 19, 2025

 
At a Glance

In this spotlight, CDC provides laboratory updates on serology testing from close contacts of a confirmed case of influenza A(H5) virus infection in a child in California, as well as sequencing information for A(H5) viruses related to the most recent Ohio human case. CDC also summarizes findings from recently published studies.

 
Risk Assessment

CDC recently published an updated avian influenza A(H5N1) virus risk assessment: The current risk to the general U.S. population is low. The risk to populations exposed to potentially avian influenza A(H5N1) virus-infected animals, including through contaminated surfaces or fluids, is currently assessed as moderate to high. CDC has moderate confidence in this assessment. (Moderate confidence, in this context, means that the assessment is based on credibly sourced and plausible information, but it acknowledges some information gaps or assumptions that underlie the analysis.)

 

Overview

Since April 2024, 70 human cases of avian influenza A(H5) virus infection have been reported in the United States. Of these, 41 cases were associated with exposure to sick dairy cows and 26 were associated with exposure to avian influenza A(H5N1) virus-infected poultry. The source of the exposure in 3 cases, could not be determined. To date, human-to-human transmission of influenza A(H5) virus has not been identified in the United States. The immediate risk to the general public from H5 bird flu remains low.

On the animal health side, USDA is reporting that since March 2024, 989 dairy herds in 17 U.S. states have confirmed cases of avian influenza A(H5N1) virus infections in dairy cows as the number of affected herds continues to grow. USDA reports that since April 2024, there have been avian influenza A(H5) virus detections in 336 commercial flocks and 207 backyard flocks, for a total of more than 90.9 million birds affected.

 

Recent Updates
  • CDC completed serology testing on blood specimens from close contacts of a child with mild illness in San Francisco who was confirmed to be positive for avian influenza A(H5N1) virus, though, there were no known animal exposures associated with that case. Serology testing was conducted to look for antibodies to influenza A(H5N1) virus in this child, which would indicate recent infection. The child's blood was tested and found to have antibodies to avian influenza A(H5N1) virus. None of the close contacts of the case in San Francisco who were tested had antibodies to avian influenza A(H5N1) virus, which supports the conclusion that none of these close contacts were infected, and that no person-to-person spread occurred among these close contacts. These findings are reassuring. To date, human-to-human transmission of influenza A(H5) virus has not been identified in the United States.
  • CDC has sequenced the virus from the most recent Ohio human case. Genetic data have been posted in GISAID (Epi ID 19785793) and have been submitted to GenBank. Sequencing indicates this is a clade 2.3.4.4b virus of the D1.3 genotype based on classification using USDA's genotyping assignment criteria. D1.3 viruses, like D1.1 viruses, originated from A3 genotype A(H5N1) viruses that were introduced to North America in 2022 and have subsequently reassorted with North American wild bird avian influenza viruses. There were no markers that would impact the effectiveness of influenza antivirals or existing candidate vaccine viruses. Finally, CDC did not identify changes that would make this virus better adapted to spread among or infect mammals. Attempts to isolate this virus in eggs are ongoing.
All CDC A(H5N1) Bird Flu Response Updates

CDC H5N1 Technical Reports

CDC H5N1 Technical Reports

These technical reports are intended for scientific audiences. Additional information for scientific audiences and the general public is available on CDC’s Information on Bird Flu webpage.

 
Latest Technical Report: June 9, 2024

Technical Report: June 2024 Highly Pathogenic Avian Influenza A(H5N1) Viruses

This report provides an update to the April 26, 2024, report to include three additional sporadic human cases (1 in Australia and 2 in the United States) and recent activity in wild birds, poultry, and other animals, including the multi-state outbreak in U.S. dairy cattle, and updated information on monitoring for human infections with highly pathogenic avian influenza A(H5N1) virus infections in the United States.

CDC continues to believe that the overall risk to human health associated with the ongoing outbreaks of highly pathogenic avian influenza A(H5N1) viruses has not changed and remains low to the U.S. general public at this time.

Previous H5N1 Technical Reports