On This Page
- Background
- Domestic Summary
- Global Summary
- Risk to Humans
- Other Documented Mammalian Infections
Background
While rare, mammals can be infected with highly pathogenic avian influenza (HPAI) A(H5N1) (“H5N1 bird flu”) viruses. Reports of these sporadic infections in mammals have occurred globally amid widespread outbreaks of bird flu infections in wild birds and poultry.
Mammals can be infected with H5N1 bird flu viruses when they eat infected birds, poultry, or other animals and/or if they are exposed to environments contaminated with virus. Spread of H5N1 bird flu viruses from mammal to mammal is thought to be rare, but possible.
Domestic Summary
In the United States, since 2022, USDA APHIS has reported HPAI A(H5N1) virus detections in more than 200 mammals. Most recently in the United States, HPAI A(H5N1) bird flu has been found in goats and cattle. A multi-state outbreak of HPAI A(H5N1) bird flu in dairy cows was first reported on March 25, 2024. This is the first time that these bird flu viruses were found in cattle. CDC confirmed one human HPAI A(H5N1) infection that had exposure to dairy cattle in Texas that were presumed to be infected with the virus. While thought to be rare, this exposure to HPAI A(H5N1) bird flu virus is the first instance of likely mammal to human transmission.
Related Links:
USDA resources
- USDA Confirms Highly Pathogenic Avian Influenza in Dairy Herd in New Mexico | Animal and Plant Health Inspection Service
- USDA, FDA and CDC Share Update on HPAI Detections in Dairy Cattle | Animal and Plant Health Inspection Service
- Federal and State Veterinary, Public Health Agencies Share Update on HPAI Detection in Kansas, Texas Dairy Herds | Animal and Plant Health Inspection Service (usda.gov)
- Highly Pathogenic Avian Influenza (HPAI) Detections in Livestock | Animal and Plant Health Inspection Service (usda.gov)
- Influenza: Not Just for the Birds (usda.gov) [286 KB, 1 page]
- APHIS Recommendations for Highly Pathogenic Avian Influenza (HPAI) H5N1 Virus in Livestock For State Animal Health Officials, Accredited Veterinarians and Producers April 2, 2024 [214 KB, 4 pages]
FDA resources
- Questions and Answers Regarding Milk Safety During Highly Pathogenic Avian Influenza (HPAI) Outbreaks | FDA
- Questions and Answers Regarding the Safety of Eggs During Highly Pathogenic Avian Influenza Outbreaks | FDA
CDC resources
- Highly Pathogenic Avian Influenza A (H5N1) Virus Infection Reported in a Person in the U.S. | CDC Online Newsroom | CDC
- Bird Flu in Pets and Other Animals | Avian Influenza (Flu) (cdc.gov)
- Technical Update: Summary Analysis of Genetic Sequences of Highly Pathogenic Avian Influenza A(H5N1) Viruses in Texas (cdc.gov)
- Highly Pathogenic Avian Influenza A(H5N1) Virus in Animals: Interim Recommendations for Prevention, Monitoring, and Public Health Investigations | Avian Influenza (Flu) (cdc.gov)
- Health Alert Network (HAN) – 00506 | Highly Pathogenic Avian Influenza A(H5N1) Virus: Identification of Human Infection and Recommendations for Investigations and Response (cdc.gov)
Global Summary
Globally, sporadic HPAI A(H5N1) virus infections in mammals have been reported across the continents of Asia, North America, South America, and Europe. More information about the global impact of avian influenza can be found here: Avian Influenza – WOAH – World Organisation for Animal Health
Specifically, recent HPAI A(H5N1) infections in mammals have been detected in sea lions in Peru and Chile, sea elephants in Argentina, and foxes in Canada, France, and other countries. A list of significant HPAI outbreaks, including in mammals, can be found here: Highlights in the History of Avian Influenza (Bird Flu) Timeline – 2020-2024 | Avian Influenza (Flu) (cdc.gov)
Risk to Humans
The wide geographic spread of HPAI A(H5N1) viruses in wild birds, poultry, and some other mammals could create additional opportunities for people to be exposed to these viruses. Therefore, there could be an increase in sporadic human infections resulting from bird and animal exposures, even if the risk of these viruses spreading from birds to people has not increased. CDC believes the current risk to the general public from bird flu viruses is low. People who have job-related or occupational exposure to infected birds or animals are at greater risk of contracting HPAI A(H5N1) virus. CDC has recommendations related to testing, treatment of HPAI A(H5N1) infection and prevention of exposure to these viruses: Highly Pathogenic Avian Influenza A(H5N1) Virus in Animals: Interim Recommendations for Prevention, Monitoring, and Public Health Investigations | Avian Influenza (Flu) (cdc.gov)
Other Documented Mammalian Infections
In recent years, HPAI H5N1 infections have been detected in mammals including but not limited to wild or feral animals such as foxes, bears, and seals; stray or domestic animals such as cats and dogs; farm animals, such as goats, cows, and mink, and zoo animals such as tigers and leopards. A timeline, which includes mammalian detections of bird flu, can be found here: Highlights in the History of Avian Influenza (Bird Flu) Timeline – 2020-2024 | Avian Influenza (Flu) (cdc.gov)
Top of Page
