New confirmed cases of HPAI in U.S. dairy cattle can be found here.

The CAHSS Dairy Network webpage has a collection of Canadian, US and international resources here.

June 25, 2025

Between Sept. 16, 2024, and June 25, 2025, FSIS collected and tested 600 diaphragm muscle samples from culled dairy cows. One dairy cow, as well as the kidney from that animal, indicated a positive for H5N1 Influenza A at very low levels. For additional details click HERE. The culled dairy cow sampling will continue until Sept. 30, 2025 as per the USDA FSIS Notice.

May 24, 2024

USDA’s Food Safety and Inspection Service (FSIS), as part of its ongoing efforts to ensure the safety of the food supply, has conducted tests on beef tissue from 96 cull dairy cows condemned at select FSIS-inspected facilities. Meat from condemned cows is prohibited from entering the food supply. On May 22, 2024, viral particles were detected in tissue samples, including muscle, from one cow. To date, samples from 95 cows have tested negative for viral particles. No meat from these dairy cattle entered the food supply.

As part of this study, FSIS collected multiple tissues, including muscle samples from the diaphragm, at FSIS-inspected slaughter facilities from cull dairy cattle that have been condemned for systemic diseases. The samples were analyzed by APHIS using PCR to determine presence of viral particles. PCR testing does not differentiate between live virus or fragments.

FSIS and APHIS are working together to conduct traceback, including notification to the producer to gather further information.

FSIS personnel identified signs of illness in the positive animal during post-mortem inspection and prevented the animal from entering the food supply. This type of inspection is part of routine FSIS operations. These actions provide further confidence that the food safety system we have in place is working.

Further updates will be provided as testing is completed.  LINK

A Canadian study reported serological evidence or HPAI H5N1 in invasive wild pigs captured in Alberta between 2021 - 2024. Seropositive samples (4.17%, 5/120) coincided with the HPAI epizootic that affected wild species and domestic poultry in Alberta, suggesting interspecies transmission of HPAI H5N1 to wild pigs (Ley Garcia et al., 2025)

 

October 2024: USDA Announces the Detection of H5N1 in a Backyard Pig in Oregon- The pig was from a small herd of swine (5 pigs) that shared water sources, housing and equipment with sheep, goats, and a small poultry flock. The poultry tested positive for H5N1 and were de-populated.  Having been noted to be scavenging on dead wild birds, the pigs were euthanized and tested. Sheep and goats at the farm are under surveillance. The Influenza A strain isolated from the infected poultry on-farm is the circulating wild bird strain, NOT the one occurring in dairy cattle in the US. (LINK)

 

A case study in Italy identified antibodies to H5N1 but negative PCR nasal swabs in free-ranging pigs that cohabitated with poultry (Rosone et al., 2023).

A 2025 Canadian study demonstrated that dairy- and avian- origin HPAI A(H5N1) infected goat respiratory and mammary cells, caused severe mastitis with marked drop in milk production and changes in milk quality, and that viruses shed in milk infected suckling kids. (Alkie et al., 2025)  

 

Antibodies to H5 avian influenza were detected in sheep in Norway nearly a year after sheep were exposed to contaminated grazing areas by a major seabird die-off. (Hol Fosse et al., 2025).

 

HPAI (H5N1) was confirmed in a sheep in England on March 24, 2025, following repeat positive milk testing. The sheep was identified following routine surveillance as it was located on a premises with infected captive birds. (UK’s Department for Environment, Food & Rural Affairs, 2025).

 

USDA’s National Veterinary Services Laboratories confirmed highly pathogenic avian influenza (HPAI) in neonatal goat kids that demonstrated neurologic signs from a Minnesota backyard premises recently affected with HPAI. The goats on the premises shared the same pasture and sole water source with infected ducks and chickens. The goats began to kid days after the birds were depopulated. Of 10 goat kids that have died (5 to 9 days of age), five tested positive on brain and other tissues for H5N1 clade 2.3.4.4b virus. Sequencing showed that isolates from the first goat and infected poultry were highly related. LINK

 

USDA detection of HPAI in mammals- Link to HPAI detections in the U.S. since May 2022, including cases in domestic cats.

 

CAHSS Information document for veterinarians with regards to influenza A(H5N1) and cats. LINK

 

"Highly Pathogenic Avian Influenza A(H5N1) Virus Infection of Indoor Domestic Cats Within Dairy Industry Worker Householders - Michigan, May 2024" (CDC MMWR, 2025). "HPAI A(H5N1) virus was detected in two indoor domestic cats with respiratory and neurologic illness that lived in homes of dairy workers but had no known direct exposure to HPAI A(H5N1)–affected farms. Both dairy workers declined testing; other household members received negative test results for influenza A."

 

Testing of sick cats on some affected dairy farms in Texas and Kansas for H5N1 has so far yielded three H5N1 (HPAI) positives. This isn’t the first time the virus has been detected in cats (e.g. they’ve been reported before in the US, Poland, and South Korea) but does suggest they should be kept away from sick cattle. LINK

The National Veterinary Services Laboratories (NVSL) confirmed the detection of Highly Pathogenic Avian Influenza (HPAI) H5N1 in alpacas from a premises where HPAI-affected poultry were depopulated in May 2024. While this HPAI confirmation is not unexpected due to the previous HPAI detection on the premises, the high amount of virus in the environment, and co-mingling of multiple livestock species on-farm, it is the first HPAI detection in alpacas.  NVSL has confirmed that the viral genome sequence for these samples is the same sequence currently circulating in dairy cattle (B3.13), which is consistent with sequences from the depopulated poultry on this premises. (LINK)

The Canadian Wildlife Health Cooperative (CWHC) maintains a dashboard of HPAI cases in wildlife (avian and mammals)

 

USDA-APHIS host an updated map of non-livestock detections LINK

November 21, 2025. A Washington State patient died of complications from HPAI H5N5. Sampling identified HPAI in the environment of the patient's small poultry flock, making exposure to domestic poultry, their environment or wild birds the most likely source of exposure for this patient.(LINK)

November 14, 2025. The first global human case of HPAI A(H5N5) was reported in Washington State,. The patient, an older individual with underlying health conditions, was hospitalized. The patient has a mixed small poultry flock that had exposure to wild birds.

March 13, 2025. The CDC released a Morbidity and Mortality Weekly Report (MMWR) on the 38 cases of HPAI A(H5N1) viruses in California during September 30 to December 24, 2024. Thirty-seven cases were dairy farm workers with occupational exposure to sick cows. LINK

February 27, 2025. There are currently 70 human confirmed cases of influenza A(H5) and one death. Forty-one cases (58%) were associated to exposure to dairy cattle herds and 24 (34%) to poultry farms and culling operations. Two cases were associated with exposure related to other animals such as backyard flocks, wild birds, or other mammals. Three cases had unknown exposure sources. LINK

February 26, 2025. "People with dairy cow or poultry exposures remain at greater risk of infection." Additional information was released for three human cases of influenza A(H5). These cases were located in Wyoming, Nevada and Ohio. LINK

Wyoming: The patient had an infected backyard flock. The patient had respiratory symptoms, underlying health conditions, was hospitalized and then discharged. The upper respiratory specimens were negative for influenza viruses, but the lower respiratory specimens were positive for avian influenza A(H5N1) virus. The virus was sequenced: avian influenza A(H5N1) virus from clade 2.3.4.4b (genotype D1.1). The virus had a genetic mutation that has previously been associated with more efficient virus replication in people and other mammals (i.e., change of PB2 E627K).

Nevada: A dairy worker with exposure to infected dairy cows had conjunctivitis and has recovered. The virus sample from this case was sequenced: avian influenza A(H5N1) virus clade 2.3.4.4b (genotype D1.1). The virus had a genetic mutation that has previously been associated with more efficient virus replication in people and other mammals (i.e., change of PB2 D701N).

Ohio: A poultry worker, exposed during culling activities on a farm with infected poultry, had respiratory symptoms and is recovering. The upper respiratory specimens were negative for influenza viruses, but subsequent specimen (site of sample collection not stated) were positive for avian influenza A(H5) virus.

December 31, 2024. Publication of a correspondence in the New England Journal of Medicine "Critical Illness in an Adolescent with Influenza A(H5N1) Virus Infection" (LINK). This correspondence describes the case of a teenager diagnosed with severe HPAI illness (genotype D1.1) in November to December 2024. 

December 9, 2024. There were 35 confirmed human cases of avian influenza A(H5N1) associated with cattle and 21 confirmed human cases associated with poultry. There were an additional 2 human cases with unknown exposure to animals. The total is currently 58 human cases. LINK.  A Californian child was affected with influenza A(H5N1) and had unknown exposure to animals LINK. The genome of the H5N1 could not be completely sequenced, but certain genes were sequenced and analyzed. These genes most closely resembled those of the B3.13 genotype from dairy cattle. LINK

The CDC is monitoring influenza in people and have not identified any unusual trends LINK.

September 9, 2024. CDC confirmed a human case of avian influenza A(H5) reported by the state of Missouri. The case was identified through that state's seasonal flu surveillance system. Missouri DHSS reports that the patient, who was hospitalized, had underlying medical conditions, was treated with influenza antiviral medications, subsequently discharged, and has recovered. There is no immediate known animal exposure. No ongoing transmission among close contacts or otherwise has been identified. This is the 14th human case of H5 reported in the United States during 2024 and the first case of H5 without a known occupational exposure to sick or infected animals. H5 outbreaks in cattle have not been reported in Missouri, but outbreaks of H5 have been reported in commercial and backyard poultry flocks and wild birds.

July 3rd, 2024.  A human case of HPAI A(H5) virus infection has been identified in the state of Colorado. This is the fourth case associated with an ongoing multistate outbreak of A(H5N1) in dairy cows and the first in Colorado. As with previous cases, the person is a worker on a dairy farm where cows tested positive for A(H5N1) virus. The person reported eye symptoms only, received oseltamivir treatment, and has recovered.  LINK

30th May, 2024- The Centers for Disease Control and Prevention (CDC) announced a third human illness from H5 avian influenza in a dairy farm worker, but unlike the earlier cases, the patient experienced respiratory symptoms, including cough without fever and eye discomfort with watery discharge. Michigan's first patient experienced eye symptoms after a direct splash to the eye from infected milk, and the second patient had direct exposure to a sick cow. "Neither individual was wearing full personal protective equipment (PPE)."

In new guidance, the US Department of Agriculture (USDA) Animal and Plant Health Inspection Service (APHIS) issued PPE recommendations for people visiting H5N1-infected herds. LINK

22 May, 2024- The Michigan Department of Health and Human Services (MDHHS) announced an H5 avian flu case in a Michigan farm worker who had regular exposure to infected livestock, marking the third human case in the United States and the second related to the H5N1 outbreaks in dairy cattle. In a statement, MDHHS said the identification of the case came after the state's ongoing public health actions allowed farm workers to monitor and notify health officials if they develop symptoms. Officials didn't detail the patient's symptoms, but said they were mild and that the farm worker has recovered..     

April 1, 2024 - A person in the United States has tested positive for highly pathogenic avian influenza (HPAI) A(H5N1) virus, as reported by Texas and confirmed by CDC. This person had exposure to dairy cattle in Texas presumed to be infected with HPAI A(H5N1) viruses. The patient reported eye redness (consistent with conjunctivitis), as their only symptom, and is recovering. The patient was told to isolate and is being treated with an antiviral drug for flu.

This infection does not change the H5N1 bird flu human health risk assessment for the U.S. general public, which CDC considers to be low. However, people with close or prolonged, unprotected exposures to infected birds or other animals (including livestock), or to environments contaminated by infected birds or other animals, are at greater risk of infection. LINK

CDC recommendations for humans to reduce risk of HPAI infection
1. Recommendations for the Public
People should avoid unprotected (not using respiratory or eye protection) exposures to sick or dead animals including wild birds, poultry, other domesticated birds, and other wild or domesticated animals, as well as with animal feces, litter, or materials contaminated by birds or other animals with suspected or confirmed HPAI A(H5N1) virus infection. People should not prepare or eat uncooked or undercooked food or related uncooked food products, such as unpasteurized (raw) milk, or raw cheeses, from animals with suspected or confirmed HPAI A(H5N1) virus infection (avian influenza or bird flu).

2. People exposed to HPAI A(H5N1)-virus infected birds or other animals (including people wearing recommended PPE) should monitor themselves for new respiratory illness symptoms, including conjunctivitis (eye redness), beginning after their first exposure and for 10 days after their last exposure.

3. Recommendations for Farmers; Poultry, Backyard Bird Flock, and Livestock Owners; and Worker Protection
To reduce the risk of HPAI A(H5N1) virus infection, poultry farmers and poultry workers, backyard bird flock owners, livestock farmers and workers, veterinarians and veterinary staff, and responders should avoid unprotected direct physical contact or close exposure with sick or dead birds or other animals, carcasses, feces, milk, or litter from sick birds or other animals potentially infected or confirmed to be infected with HPAI A(H5N1) virus. Farmers, workers, and responders should wear recommended PPE such as an N95 filtering facepiece respirator, eye protection, and gloves, and perform thorough hand washing after contact. (e.g., see: PPE recommended for poultry workers) when in direct contact with sick or dead birds or other animals, carcasses, feces, or litter from potentially infected birds or other animals, and when going into any buildings with or that have had sick or dead birds or other animals, carcasses, feces, or litter from potentially infected birds or other animals. Workers should receive training on and demonstrate an understanding of when to use PPE; what PPE is necessary; how to properly put on, use, take off, dispose of, and maintain PPE; and PPE limitations.

Biosecurity Update for On-farm Dairy Service Providers LINK

 

Dairy Biosecurity Recommendations: HPAI and more LINK

 

proAction: Canadian Dairy Quality Assurance Program Biosecurity Module LINK

 

USDA-APHIS Secure Milk Supply (SMS) Dairy Biosecurity Resources LINK

 

CAHSS Biosecurity Recommendations for Canadian Dairy Herds LINK

Canadian Food Inspection Agency: Highly pathogenic avian influenza (HPAI) in livestock LINK

 

USDA-APHIS: Detection of Highly Pathogenic Avian Influenza in Dairy Herds: Frequently Asked Questions LINK

 

USDA-APHIS: Questions and Answers Regarding Milk Safety During Highly Pathogenic Avian Influenza (HPAI) Outbreaks   LINK

• Increase avian influenza surveillance in domestic and wild birds.
• Enhance surveillance for early detection in cattle.
• Include HPAI as a differential diagnosis in non-avian species.
• Notify cases of HPAI in all animals to WOAH.
• Implement preventive and early response measures to break transmission pathways among animals.
• Protect humans in close contact with or handling sick animals.
• Avoid implementing unjustified trade restrictions.
  

LINK 

• USDA reported no real evidence that virus is replicating inside the cows aside from the udder
• hypothesis that it may be moving between cattle by indirect contact (e.g. milking equipment) instead of respiratory route (e.g. coughing) or fecal shedding.
• also a hypothesis: viruses in all affected US cows to date are so similar that they may have originated from one herd. "So potentially what we've seen so far for H5N1 disease in US dairy cows could reflect one spillover event from birds, or a couple of closely related ones, as opposed to multiple independent events in which multiple infected birds contacted multiple herds".