Skip to Main Content

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

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: July 16, 2024
Dairy Cattle: On-going multi-state outbreak Humans: 9 cases in the U.S.
Wild Birds:  Widespread Person-to-person spread: None
Poultry Flocks: Sporadic outbreaks Current public health risk: Low
Mammals:  Sporadic infections  

Latest Updates from the CDC 
  • H5 bird flu is widespread in wild birds worldwide and is causing outbreaks in poultry and U.S. dairy cows with several recent human cases in U.S. dairy and poultry workers.
  • While the current public health risk is low, CDC is watching the situation carefully and working with states to monitor people with animal exposures.
  • CDC is using its flu surveillance systems to monitor for H5N1 activity in people.

CDC A(H5N1) Bird Flu Response Updates

CDC A(H5N1) Bird Flu Response Update

The CDC provides updates on its response activities related to the multistate outbreak of avian influenza A(H5N1) virus, or "H5N1 bird flu," in dairy cows and other animals in the United States.

Latest Update: CDC A(H5N1) Bird Flu Response Update, July 12, 2024

CDC continues to respond to the public health challenge posed by a multistate outbreak of avian influenza A(H5N1) virus, or “H5N1 bird flu,” in dairy cows and other animals in the United States. CDC is working in collaboration with the U.S. Department of Agriculture (USDA), the Food and Drug Administration (FDA), state public health and animal health officials, and other partners using a One Health approach.

Four human cases of A(H5) infection associated with this outbreak in U.S. dairy cows have been reported. Based on the information available at this time, CDC’s current H5N1 bird flu human health risk assessment for the U.S. general public remains low.

On the animal health side, USDA is reporting that 151 dairy cow herds in 12 U.S. states have confirmed cases of avian influenza A(H5N1) virus infections in dairy cows as the number of infected herds continues to grow.

Among other activities previously reported in past spotlights and still ongoing, recent highlights of CDC's response to this include updates on the recent human case in Colorado:

  • Reporting that despite extensive efforts, CDC has been unable to sequence or isolate virus from the recent human case in Colorado. Attempts to sequence viral RNA from the Colorado case were unsuccessful most likely due to insufficient virus in the clinical sample.
  • As a result, CDC has not been able to conclusively determine the neuraminidase (NA) subtype of the virus.
  • Given that cows on the farm where the patient worked were confirmed positive for A(H5N1) virus infection, it is likely this was an N1 also, but that cannot be conclusively demonstrated. Virus isolation attempts in eggs and cells were similarly unsuccessful.

Previous 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