Avian influenza viruses

Highly pathogenic avian influenza (HPAI) is caused by an influenza type A virus. It can infect poultry such as chickens, turkeys, pheasants, quail, domestic ducks, geese and guinea fowl. Free-flying waterfowl such as ducks, geese and shorebirds carry the virus.

Avian influenza (AI) viruses are divided into subtypes based on the combination of 2 proteins: hemagglutinin or “H” proteins (H1–H16) and neuraminidase or “N” proteins (N1–N9). HPAI viruses are either high or low pathogenic (HPAI and LPAI), depending on the molecular characteristic of the virus and its ability to cause severe clinical signs and high mortality in domestic poultry.

Learn more about avian influenza in poultry.

Learn more about influenza viruses across domestic animal species.

Current situation

Domestic birds

During the winter 2024–2025 season, 12 poultry premises (11 commercial flocks and 1 small flock) were confirmed infected with HPAI H5N1 in southern Ontario. All flocks were destroyed and premises were placed under quarantine by the Canadian Food Inspection Agency (CFIA) as per the federal eradication policy.

HPAI has also been detected in other provinces, with the majority of cases in British Columbia. The CFIA provides updates on investigations and orders of avian influenza in domestic birds by province.

Spring and fall are high-risk periods due to wild bird migration. This increases the concentration of the virus in the environment for a prolonged period of time. It is recommended to keep all domestic poultry indoors during these periods when possible.

Other seasonal activities which involve birds from different premises, such as fairs, shows, sales, competitions and swap meets, are also considered high risk for HPAI and should be avoided.

It is generally recommended that bird owners not allow people who have recently been in contact with other birds (such as their own or attending a bird sale or show) to enter the housing area or handle birds.

Livestock

There have been no detections of HPAI in cattle or other livestock species in Ontario or Canada to date.

A multi-state outbreak of HPAI H5N1 in dairy cows has been ongoing in the United States since March 2024. To date, nearly 1,000 dairy herds in 17 states have been confirmed infected. The same virus strain have also been reported in farm workers, barn cats, domestic cats and poultry flocks. The initial source of infection for cattle in 2024 is believed to be a single transmission event from wild birds.

Additional cattle and herds were infected through:

  • contaminated milking equipment
  • the movement of infected cattle
  • the movement of infected equipment, vehicles or shared workers between infected and non-infected premises

In 2025, second and third spillover events of a different strain of HPAI H5N1 to dairy cattle from wild birds were detected in the U.S. in Nevada and Arizona.

Read the U.S. Department of Agriculture’s reports on these additional spillover events to dairy cattle in Nevada and Arizona.

Read the U.S. Department of Agriculture’s national epidemiologic brief on H5N1 in dairy cattle (PDF).

Other detections of HPAI H5N1 in U.S. livestock have included goat kids (Minnesota), alpacas (Idaho) and pigs (Oregon). These livestock were in close contact with HPAI infected poultry in a shared environment.

Wild birds and mammals

Since November 3, 2021, the Canadian Wildlife Health Cooperative (CWHC) has reported 2,537 positive HPAI detections in wild birds, including 413 in Ontario.

Find more information on detections in Canadian wildlife.

Since January 1, 2022, the USDA has reported a total of 12,587 positive HPAI detection in wild birds. In the United States, HPAI has also been reported in 521 mammals across 23 species. These numbers include detections in wild mammals and 106 domestic cats.

Additional information on detections in American wild birds and mammals.

Find more information on HPAI Detections in Wild Birds.

What to do if you find sick or dead birds/wildlife on your property

You should report any sick or dead birds/wildlife found on your property to the Canadian Wildlife Health Cooperative. They may arrange for submission of wildlife for HPAI testing at the University of Guelph’s Animal Health Lab. You can report any findings:

The recommendation to the public and pet owners continues to be to avoid direct contact with alive or dead wildlife, stray animals or wild birds.

If you must handle wildlife, follow the guidance on protecting yourself when handling sick, injured or orphaned wildlife.

Clinical signs

HPAI is a federally reportable disease in any species. Producers should report clinical signs or suspected illness in their flocks or herds to their veterinarian immediately. If veterinarians suspect HPAI in poultry or other species, they must report it to their local CFIA district office.

Clinical signs of HPAI in domestic poultry may include:

  • decrease in feed and water consumption
  • extreme depression
  • drop in egg production (many of which are soft-shelled or shell-less)
  • high and sudden morbidity and mortality rate
  • signs of septicemia (hemorrhages on the hocks, hemorrhagic enteritis, severe edema of eyelids, wattle and combs)

Clinical signs of HPAI in dairy cattle may include:

  • sudden reduced milk production
  • thickened or colostrum-like milk
  • decrease in feed consumption or drop in rumen motility
  • respiratory signs, including clear nasal discharge
  • dry manure or diarrhea
  • fever
  • lethargy
  • dehydration

Veterinary guidance for testing of suspect cases or for clinically normal cattle for producer biosecurity decisions is available from the CFIA.

Food safety/zoonotic risk

Avian influenza is not a food safety risk, but consumption of undercooked meat or unpasteurized (raw) milk products from infected animals could pose a risk of virus transmission. American and Canadian pasteurization studies support that commercially sold milk and milk products remain safe to consume. The pasteurization process kills harmful bacteria and viruses, including HPAI, ensuring milk and milk products are safe to drink and eat. In Canada, milk must be pasteurized before sale. Raw (unpasteurized) milk products should not be fed to pets or livestock.

Avian influenza is not a significant public health concern for people who are not in direct contact with infected birds or animals. To date, testing in the U.S. has not identified changes to the virus that would make it more transmissible to humans. This indicates that the risk to the public remains low, and no sustained human-to-human transmission of HPAI has been reported anywhere in the world. However, a small number of U.S. farm workers have been infected following exposure to infected cattle or poultry. Most of these infected people displayed mild symptoms before recovering. In 2025, there was 1 death in a person hospitalized for HPAI H5N1, a senior in Louisiana who had underlying medical complications and was exposed to backyard flocks and wild birds.

AI viruses can infect people via eyes, nose or mouth, or if the virus is inhaled through aerosol suspension. This is of concern for people who are unprotected when in routine contact with infected birds or contaminated surfaces. Farm workers with risk of exposure to HPAI-infected animals should take appropriate precautions and use personal protective equipment.

While the annual human influenza vaccine does not protect against HPAI, it will help prevent you from getting seasonal influenza, which could weaken your immune system or resistance to other infections.

Questions or concerns about human health and HPAI should be directed to your local public health unit or your healthcare provider.

Signs of illness in humans

Based on studies of patients with the HPAI H5N1 virus, signs of illness in humans can range from very mild to severe. The most common signs include:

  • fever
  • cough
  • conjunctivitis (red eyes)
  • sore throat
  • runny or stuffy nose
  • muscle or body aches
  • headaches
  • fatigue or tiredness
  • shortness of breath or difficulty breathing

Less commonly, diarrhea, nausea, vomiting or seizures can occur. Diarrhea is more common with avian influenza than with influenza due to human viruses.

It is important to tell your healthcare provider or local public health unit if you have any of these signs or if you have been around or in contact with suspected or confirmed HPAI animals in the past 10 days. Anti-viral therapy may be recommended and prescribed to you. If you are showing signs, specific tests to detect avian influenza in people are available.

If you do not have access to a healthcare provider, please contact Health811 by calling 811 or using the live chat feature.

Biosecurity

Ongoing poultry and livestock HPAI detections emphasize the continued importance of biosecurity measures across species.

In response to the U.S. dairy cattle outbreak, the CFIA has enhanced import controls and introduced additional measures for Canadian cattle returning from the U.S. to prevent the introduction of HPAI to Canadian dairy cattle. They have also conducted surveillance initiatives nationally on retail (pasteurized) and processor (raw) milk products.

Additional information

Human health

United States

European Union