Avian influenza, 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 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.
The severity of the illness in birds (i.e., whether the avian influenza virus is considered LPAI or HPAI) does not predict severity in humans. For instance, influenza A(H7N9) viruses are LPAI but can cause severe illness and even death in humans that are infected. Therefore, precautions should be taken regardless of the severity of illness in birds.
Avian influenza 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 wild and domestic animal species.
Since 2022, there has been unprecedented global spread of highly pathogenic avian influenza A (H5N1 and related viruses) in many wild bird species and domestic poultry. There have been spillover infections to mammals, including foxes, skunks, marine animals, goats, and cows, as well as sporadic infections in humans. While influenza A virus infections have been occasionally observed in cows, in March 2024, avian influenza A(H5N1) was detected in goats and dairy-producing cattle in several US states for the first time. Unpasteurized milk from some sick cattle also tested positive for the virus. Sporadic human cases of H5N1 have been detected in
persons exposed to infected dairy cattle in the US.
Influenza viruses are adaptable and can change markedly when strains from humans or different animal species mix and exchange genetic information. Avian influenza could become more serious if the virus develops the ability to spread from person to person.
The current strain of avian influenza A(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. This could include persons with occupation- or recreation- related exposure to infected commercial and domestic poultry as well as other infected birds or mammals.
For more information on the current human case in B.C., see the
news release.
On November 9, 2024 a case of H5N1 was reported in a teen in Fraser Health region (see the above news release for more information). Genomic sequencing results from this case indicated that the virus is related to the H5N1 avian influenza viruses from the ongoing epizootic in British Columbia (Influenza A (H5N1). clade 2.3.4.4b, genotype D.1 .1). The genome has a E627K mutation in the PB2 gene, which has previously been observed in other human and mammalian infections.
Avian influenza is closely monitored in birds, mammals, and people due to the potential for the virus to change and gain the ability to spread easily between people.
There have been avian influenza transmission events observed in a wide range of wild mammalian species around the world such as foxes, sea lions, and skunks. These may have been caused by direct contact with infected wild birds, scavenging on infected carcasses, or indirectly through contaminated environments. Mammal-to-mammal transmission is rare, but may, for example, have occurred in Peru between sea lions. In BC, several detections of avian influenza have been reported in foxes, raccoons, 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 or contact the BC Wildlife Health Program at 250-751-7246.
While the risk of transmission to humans is low, workers, and others who have contact with birds or wildlife, especially sick or dead animals should take precautions, such as wearing personal protective equipment and washing their hands. Advice on safe handling of wild animals can be found here:
Wildlife exposure precautions for avian influenza.
Information for poultry owners and workers (October 2024)
Poultry flocks in Canada are usually free of avian influenza viruses. However, sometimes commercial or backyard birds become infected with avian influenza viruses through direct contact with infected wild birds or other infected poultry, or through contact with surfaces, feed, or water that have been contaminated with the viruses through infected bird feces or other secretions.
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 BC, 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 and 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 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.
Other types of farmed animals may also develop illness due to avian influenza, including ruminants such as dairy cows and goats, farmed mink, foxes and raccoon dogs. Mammal-to-mammal transmission is rare, but is occuring between cattle in the United States, and may have occured during an H5N1 outbreak in Spain between farmed minks.
For more information on precautions for ruminants see the Canadian Food Inspection Agency’s page on ruminants and avian flu and the National Biosecurity Standards animal biosecurity page.
Avian influenza viruses usually do not infect humans and do not spread easily from person-to-person. Rare cases have been reported, most often in people who had close unprotected contact with infected poultry, cattle, or environments heavily contaminated with the virus. The virus can enter the body through their mouth, eyes, or nose.
From 2003 – July 19, 2024, 896 H5N1 cases, including 463 deaths, were reported to the WHO as reported here:
WHO AI human cases 2003-2024. Several infections
have been detected in North America in the recent A(H5N1) outbreak which were not considered serious.
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.
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.
The risk of infection is low for the general public who has limited contact with infected animals and their environments, but the following measures can help prevent infection:
- Avoid touching sick or dead birds and animals.
- Limit exposure to poultry farms or bird markets
- Follow good hand hygiene practices, 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 or other products from game birds, poultry, or other animals infected with avian influenza. 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.
Multiple safeguards in commercial poultry and dairy supplies help to ensure that the risks of exposure to avian influenza viruses through commercial food products are minimized. It is safe to eat properly handled and cooked poultry and dairy products.
In Canada, commercial birds from farms affected by avian influenza outbreaks are humanely culled and disposed of therefore do not enter the marketplace. Poultry and poultry products (like eggs) should be
handled and cooked properly, which will kill bacteria such as Salmonella, and viruses, including bird flu viruses.
In March 2024, unpasteurized milk from cattle infected with avian influenza tested positive for A(H5N1) in the US. In Canada, only milk from healthy dairy cattle or other livestock enters the commercial milk supply chain. Further, pasteurization of commercial milk products kills pathogens, including influenza viruses that may be present. Pasteurized milk and milk products, including pasteurized cheeses, are safe to consume. Consumers should avoid consumption of unpasteurized milk see the
Dairy Safety page for more information.
