USDA Confirms New H5N1 Avian Flu Cases in Mammals and Wild Birds as Poultry and Dairy Cases Plateau

The U.S. Department of Agriculture’s Animal and Plant Health Inspection Service (APHIS) has confirmed additional detections of highly pathogenic avian influenza (H5N1) in mammals and wild birds. While the pace of new cases in commercial poultry and dairy cattle has slowed, the virus continues to circulate in wildlife across the country, including in species not traditionally associated with avian influenza.

New Mammalian Cases Raise Concern

Among the four newly reported mammalian H5N1 infections:

• A desert cottontail rabbit from Maricopa County, Arizona, was sampled in May, around the same time as the county’s large-scale poultry outbreaks.

• A red fox from Costilla County, Colorado, was sampled on May 29, marking another predator infected likely through scavenging or predation.

• A domestic cat from Contra Costa County, California, sampled on December 11, 2024, links to earlier outbreaks involving raw pet food and unpasteurized milk.

• A muskrat from Saratoga County, New York, sampled in January, highlights the virus’s persistence in semi-aquatic wildlife.

These findings underscore the ongoing risk of interspecies transmission, including in companion animals, which may be exposed through raw diets or environmental contact with infected wildlife or livestock.

Wild Bird Surveillance Continues

APHIS also reported 75 new detections of H5N1 in wild birds, the majority of which were sampled during winter months. Notably, recent positives include birds collected in Maricopa County, Arizona—the epicenter of the spring poultry outbreak. Species include grackles, pigeons, and various perching birds. In the East, a Canada goose from Cecil County, Maryland, also tested positive, suggesting continued geographic spread.

Veterinary and Public Health Implications

While no recent spikes in domestic poultry or cattle have been reported, the USDA has confirmed:

• 1,073 total H5N1 infections in dairy cows across 17 states (latest as of June 3)

• Most recent poultry detection on June 11

Veterinarians, especially those in mixed-animal and dairy practice, are advised to remain alert for signs of respiratory illness in livestock and to report any unusual deaths in wildlife or companion animals. Pathogens like H5N1, which cross species barriers, require a coordinated One Health approach involving veterinary, wildlife, and public health sectors.

FAQs: H5N1 and Veterinary Relevance

What is H5N1 avian influenza?
H5N1 is a highly pathogenic virus affecting birds, mammals, and occasionally humans. It spreads via direct contact, contaminated environments, and ingestion of infected materials.

How does H5N1 affect mammals?
In mammals, especially scavengers or predators, the virus can cause neurologic or respiratory symptoms and is often fatal. Domestic cats are at risk if fed raw poultry or dairy.

Is there a risk to humans?
Though rare, human infections can occur, typically through contact with infected birds or contaminated environments. There are currently no confirmed cases linked to milk or meat from infected cattle.

Can veterinarians test for H5N1?
Yes. State veterinary diagnostic labs and USDA-approved labs can test samples from suspected cases. Testing is especially important for dairy cattle, poultry, and wildlife.

How should pet owners respond?
Avoid feeding pets raw meat or unpasteurized dairy products. Keep pets indoors and away from sick or dead birds.