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Avian Influenza

Current H5N1 Bird Flu Situation in Cattle

Background of Current Outbreak

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 had been found in cows. 

On April 1, CDC confirmed one human HPAI A(H5N1) infection in a person with exposure to dairy cows in Texas that were presumed to be infected with the virus. This is thought to be the first instance of likely mammal to human spread of HPAI A(H5N1) virus. In May 2024, CDC began reporting additional, sporadic human cases in people who had exposure to infected dairy cows.

That latest human case counts are available at H5N1 Bird Flu: Current Situation Summary | Avian Influenza (Flu) (

H5N1 in Mammals

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.

In the United States, since 2022, USDA APHIS has reported HPAI A(H5N1) virus detections in more than 200 mammals.