Avian influenza (AI) viruses

Highly pathogenic avian influenza (HPAI) is caused by an influenza type A virus. It can infect free-flying waterfowl and domestic poultry, but it can also infect various wild and domestic mammals (cats, dogs, cattle, foxes, skunks) and rarely, humans. Domestic poultry susceptible to HPAI infections are:

  • chickens
  • turkeys
  • pheasants
  • quail
  • domestic ducks
  • geese
  • guinea fowl
  • pigeons

Wild birds 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). AI 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

As of April 3, Ontario’s single domestic commercial poultry HPAI case is a holdover from the fall migration season, with no infections detected so far during the 2026 spring migration season.

HPAI has been detected in other provinces, with the majority of cases in British Columbia and Nova Scotia. The Canadian Food Inspection Agency (CFIA) provides updates on investigations and orders of avian influenza in domestic birds by province.

When HPAI is detected on a premises:

  • all flocks on premises are humanely euthanized
  • the CFIA places the premises under quarantine as per the federal eradication policy

Seasonal risk: The fall through to late spring is the high-risk period because of wild bird migration events and thawing of frozen HPAI positive wild birds on the landscape. This increases the amount of virus present in the environment during this time.

To limit your flock’s risk:

  • keep domestic poultry indoors during spring and fall migration when possible
  • avoid activities that mix birds from different premises such as fairs, shows, sales, competitions and swap meets
  • don’t allow people who have recently handled other birds to handle your birds or enter the birds’ housing area

Livestock

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

In the United States, a multi-state outbreak of HPAI H5N1 in dairy cows began in March 2024. To date:

  • more than 1,000 dairy herds in 19 states have been confirmed infected
  • the same virus strain has been reported in farm workers, barn cats, domestic cats, domestic dogs and poultry flocks
  • other detections include goat kids (Minnesota), alpacas (Idaho) and pigs (Oregon) — all were in close contact with infected poultry

The initial source of infection in cattle is believed to be a small number of transmission events from wild birds. As a result of these spillover events, additional cattle and herds were infected through:

  • contaminated milking equipment
  • movement of infected cattle
  • movement of infected equipment, vehicles or shared workers between premises

For more information, read the U.S. Department of Agriculture’s (USDA) national epidemiologic brief on H5N1 in dairy cattle (PDF).

In January 2026, 5 Dutch dairy cows from one farm showed evidence of past exposure (antibodies) to HPAI, but no active virus. The cows were detected during follow-up testing prompted by detection of HPAI in farm cats, suggesting a previous, self-limited spillover event.

Wild birds and mammals

Since November 3, 2021, the Canadian Wildlife Health Cooperative (CWHC) has reported 3,567 positive HPAI detections in wild birds, including 680 in Ontario.

Find more information on detections in Canadian wildlife.

Since January 1, 2022, the USDA has reported positive HPAI detections in 18,755 wild birds and 707 mammals across 23 species, including 153 domestic cats.

Additional information is available on detections in American wild birds and mammals.

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

Report any sick or dead birds or wildlife on your property to the Canadian Wildlife Health Cooperative. They may arrange for testing at the University of Guelph’s Animal Health Lab.

You can report any findings by calling 1-866-673-4781 or emailing on-nu@cwhc-rcsf.ca.

Avoid direct contact with live or dead wildlife and 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 if detected in any domestic species.

Producers: Report clinical signs or suspected illness in your flock or herd to your veterinarian immediately.

Veterinarians: If you suspect HPAI in poultry or other species, report it to your 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
  • reduced feed intake or 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 and zoonotic risk

AI is not a food safety risk when meat and milk are properly cooked or pasteurized.

  • American and Canadian studies have shown that pasteurization kills harmful bacteria and viruses, including HPAI.
  • In Canada, milk must be pasteurized before sale.
  • Do not feed raw (unpasteurized) milk products to pets or livestock.

AI is not a significant public health concern for people who are not in direct contact with infected birds or animals.

  • U.S. testing shows no changes that make the virus more transmissible to humans.
  • No sustained human-to-human transmission has been reported worldwide.
  • A small number of U.S. farm workers have been infected after exposure to infected cattle or poultry. Most had mild symptoms and recovered.
  • In 2025, 2 deaths occurred in the United States in people with underlying health issues who had contact with backyard flocks and wild birds.
  • There was one death in Mexico attributed to HPAI.

AI viruses can infect people through the eyes, nose, mouth or inhalation. Farm workers with risk of exposure to HPAI-infected animals should take appropriate precautions and use personal protective equipment.

The annual human influenza vaccine does not protect against HPAI, but it helps prevent the severity of seasonal flu and reduces the risk of co-infection with seasonal and avian influenza strains. Seasonal flu shots are available to Ontario residents over the age of 6 months and are encouraged for anyone working with animals.

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

Signs of illness in humans

The most common signs of HPAI H5N1 include:

  • fever
  • cough
  • red eyes (conjunctivitis)
  • 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 AI than with influenza caused by 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 HPAI detections in poultry and livestock emphasize the importance of strong biosecurity measures across species.

In response to the U.S. dairy cattle outbreak that began in 2024, the CFIA 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