Avian influenza (AI), or "bird flu," is a contagious viral infection. It is caused by Type A influenza viruses. It primarily affects birds but can infect humans and other mammals. Influenza viruses, including avian, are classified into subtypes based on the two proteins on their surface, haemagglutinin (H) and neuraminidase (N) for example H5N1, H7N9. Avian Influenza is designated as highly pathogenic (HPAI) when it causes illness and mortality in infected poultry.
These viruses occur naturally among wild aquatic bird species and can spillover to other wild bird species, domestic birds such as chickens and turkeys, pet birds, and other animal species.
Since 2022, there has been unprecedented global spread of highly pathogenic avian influenza (H5N1) in many wild bird species and domestic poultry with occasional spillover to mammals (e.g. foxes, skunks, marine animals).
However, influenza viruses are changeable; when strains from humans or different animal species mix and exchange genetic information, it could become more serious if the virus develops the ability to spread from person to person.
The current strain of avian influenza (H5N1) circulating in birds in North America poses low risk to the public; however, those who come into contact with sick birds or other animals have an increased risk and should take precautions.
AI viruses can be broadly classified into two types:
- Low pathogenic avian influenza (LPAI) Most avian influenza viruses are low pathogenic. These cause little or no signs of illness in birds.
- Highly pathogenic avian influenza (HPAI) viruses can cause severe illness and death in birds.
However, the severity of the illness in poultry (i.e. whether the avian influenza virus is considered LPAI or HPAI) does not predict severity in humans. For instance, A (H7N9) viruses are LPAI but cause severe illness and even death in a large proportion of humans that are infected. Therefore, precautions should be taken regardless of pathogenicity in birds.
Wild aquatic birds, including gulls, terns, ducks, geese, and swans, are the natural reservoir (hosts) of virtually all influenza A subtypes. Usually these viruses rarely cause illness or death in wild birds; however with the current strain of avian influenza, wild birds are becoming ill and dying in greater numbers. Avian influenza can spread to domestic poultry following direct contact with infected wild birds or indirectly through contaminated environments. Members of the public should avoid touching sick or dead birds and report dead birds to the BC Wild Bird Mortality Line (1-866-431-2473). For sick/dead mammals, contact the BC Wildlife Health Program at 250-751-7246. More information can be found here: BC Wildlife Health Fact Sheet April 2022
Avian influenza detections in wild birds/animals in Canada are posted on the CFIA's avian influenza wildlife dashboard.
Additionally, there have been avian influenza transmission events observed in several mammal species around the world in species such as foxes, mink, sea lions, and skunks. There is evidence suggesting mammal-to-mammal transmission during an H5N1 outbreak in Spain with farmed minks as well as in Peru with sea lions. In British Columbia, several detections of avian influenza have been reported in foxes and skunks. Wild mammals infected with avian influenza may show signs of neurological illness such as seizures, tremors, circling, excess salivation, or inability to walk.
People who encounter a sick or dead wild animal should leave the animal where it is and contact a BC wildlife professional.
While the risk of transmission to humans is low, workers who come in contact with birds or wildlife, especially sick or dead animals need to take precautions, such as personal protective equipment and hand hygiene, to protect themselves which can be found here: Wildlife exposure precautions for avian influenza
Poultry flocks in Canada are usually free of avian influenza viruses. However, sometimes domesticated birds become infected with avian influenza viruses through direct contact with infected wild birds or other infected poultry, or through contact with surfaces that have been contaminated with the viruses.
Avian influenza viruses can spread rapidly and cause outbreaks in poultry, which lead to devastating consequences for the poultry industry. Poultry owners can experience high mortality in flocks, food security can be threatened and containment of outbreaks requires that all birds are culled on an infected farm. Avian influenza outbreaks have occurred in poultry in British Columbia, including the extensive outbreak of H7N3 between February and May 2004, the H5N2 outbreak in December 2014, the H5N1 outbreak in February 2015, and the current H5N1 outbreak that began in April 2022. The current outbreak is connected to the global spread of H5N1 among wild and domestic birds, as well as, several mammalian species. Status of ongoing avian influenza response by province - Canadian Food Inspection Agency (canada.ca) Avian influenza outbreaks in poultry are of concern for several reasons:
- the potential for low pathogenic viruses to evolve into highly pathogenic viruses
- the potential for rapid spread and significant illness and death among poultry during outbreaks of highly pathogenic avian influenza
- the economic impact and trade restrictions from an avian influenza outbreak
- the possibility that novel avian influenza A viruses with pandemic potential could be transmitted to humans
During an outbreak of avian influenza in poultry, the risk to the general public is very low. Most avian influenza viruses cannot spread easily from birds to people, or from person-to-person. However, any new influenza virus in the human population is a concern because of its potential to change and adapt for more easy transmission between people. Public health officials work closely with animal health officials to ensure that poultry producers and workers who may have to come into close contact with infected birds are protected.
Poultry owners should take steps to protect their birds, know how to recognize the signs of avian influenza, and where to report should their birds shows signs of avian influenza. See: Avian influenza (AI) - Province of British Columbia (gov.bc.ca)
Avian influenza viruses usually do not infect humans and cannot spread easily from person-to-person. Rare cases have been reported, most often in people who had close unprotected contact with infected poultry or environments heavily contaminated with the virus. From 2003 – March 3, 2023, 873 H5N1 cases, including 458 deaths, were reported to WHO and can be found here: WHO AI human cases 2003-2023
The reported symptoms of people infected with avian influenza vary from mild symptoms such as, conjunctivitis (i.e. red eyes with discharge) to influenza-like illness (i.e. fever, sore throat, muscle aches) to severe respiratory illness. Others remain asymptomatic with the virus. Whether a virus has been characterized as highly pathogenic (HPAI) or low pathogenic (LPAI) in birds does not predict the effect it may have on people. LPAI H7N9 and HPAI H5N1 have been responsible for most human illness worldwide to date, including the most serious illnesses and deaths. In January 2015, BC reported the first human cases of H7N9 in two travellers returning from China. Both cases fully recovered, and no additional human cases of H7N9 have been identified in BC. Only one human case of HPAI H5N1 has been identified in Canada (in Alberta), a fatal case that was also travel-related.
Human infections with avian influenza rarely spread to other people. There have been just a few instances of this reported among close contacts such as household members of someone who was ill with avian influenza. However, avian influenza is closely monitored in both birds and people due the potential for the virus to change and gain the ability to spread easily between people.
When the avian influenza virus infection does occur in humans, it happens most often after close, prolonged and unprotected (no masks, gloves or other protective wear) contact with infected birds and then the person touches their mouth, eyes, or nose. The risk of infection is low for the general public who has limited contact with infected animals. Taking the following measures will help in prevention of getting the bird flu:
- Avoid touching sick or dead birds and animals.
- Limit exposure to poultry farms or bird markets
- Good hand hygiene including after touching uncooked poultry
- Do not eat raw or undercooked poultry products
Pet owners should monitor their pets closely to ensure they don't come into contact with sick or dead birds and animals. They should not be fed any raw meat from game birds or poultry. If pets develop signs of illness after exposure to sick or dead animals, owners should consult with their veterinarian. For more information on precautions for pets see the CFIA's guidance on pets and avian flu.
In Canada, all birds from farms affected by avian influenza outbreaks are humanely culled and disposed of therefore do not enter the market place. All retail poultry and poultry products (like eggs) remain safe for human consumption, but they should always be handled and cooked properly because of the risks from known food-borne illnesses, like Salmonella.
