Avian influenza A(H5N1) 2022 outbreak in Canada

Since late 2021, new cases of avian influenza, more commonly known as bird flu, have been spreading among wild and farmed birds globally. Avian influenza, caused by a Type A influenza virus, is not a new disease, and sporadic outbreaks have occurred in most years over the past two decades. The current rise in cases, however, has led to bird deaths from the virus and culling of several million poultry and egg producing birds in Canada. There is concern about where the virus is spreading, how it is being tracked in Canada, and what the risks are to humans.

What is avian flu?

Avian flu is a generic term referring to zoonotic influenza viruses that can infect a range of bird species. There are many different types and subtypes, which have different levels of pathogenicity. Some of these, such as influenza A(H5) and its subtypes (e.g., influenza A(H5N1)), are known to transmit easily between different bird species, and on rare occasions pass from infected birds to humans or other mammals. The current avian flu spreading in Canada is the H5N1 highly pathogenic avian influenza (HPAI), which has a very high mortality rate of up to 90-100% among infected birds.

Where has it been detected?

The recent spread of H5N1 has been observed in wild, domestic, and commercial bird flocks globally. To date, the Canadian Food Inspection Agency (CFIA) has reported cases in both poultry and non-poultry flocks in most provinces, at both commercial and private premises, with the largest number of affected sites in Alberta and Ontario. At the time of writing, the Highly Pathogenic Avian Influenza – Wild Birds dashboard, has reported cases in about 200 wild birds, including bald eagles, snow geese, crows, and others. Two fox kits were also identified to have died from influenza A(H5N1) infection in Ontario, the first cases of Eurasian H5N1 in wild mammals detected in North America.

What is the main concern?

The primary concern is that continued transmission of the virus among wild, commercial, and domestic birds, could result in additional bird deaths, or culling of infected flocks to prevent further spread. This can have major impacts on commercial food producers, and smaller poultry holdings, including backyard chickens kept for eggs or meat. The virus can spread by direct contact between infected and healthy birds, or via surfaces, food, or water that has been contaminated by bird feces, saliva, or respiratory droplets. The virus can also be spread between farms by humans, via contamination on their boots, clothing, or equipment.

Can the virus spread to humans?

The CFIA does not consider HPAI to be a food safety concern, and the risk of transmission from birds to humans is very low, particularly for people who have no contact with birds, either wild or domestic.  While transmission to humans is rare, increased spread among wild birds and poultry increases the possibility of exposure.  Transmission to humans is usually due to direct contact between a person (e.g., a poultry worker) and an infected bird, and not due to human-to-human transmission. Persons infected with HPAI may experience initial fever and cough, which can progress to a lower respiratory disease. While cases in humans remain rare, the case fatality rate reported by the World Health Organization (WHO) is high. Between 2003 and 2021, the WHO recorded 862 human cases of avian influenza A(H5N1) and 455 deaths, equating to a cumulative human mortality rate of >50%. One of the most significant outbreaks was in Egypt in early 2015, where there were more than 125 human cases and 33 deaths.

There have been very few recent cases of avian influenza A(H5N1) in humans. One case was detected in the UK in December 2021 in a person who kept a large number of domestic birds, and one case in the US in April 2022 in a person who had contact with infected poultry. There have been no deaths associated with the current outbreak so far, and there are no indications that a high risk to humans currently exists. Any cases of human infection should be carefully monitored to identify changes in the virus and transmission patterns.

What can be done?

Measures to reduce the spread of avian influenza among commercial producers are set out by industry regulators and federal agencies, and can include specific biosecurity measures such as protecting flocks from exposure to wild birds, reporting of sick or dead birds, practicing good hygiene protocols, and testing by agencies such as the CFIA.

Practical actions for people who keep small flocks or pet birds on private property include taking measures to reduce contact with wild birds, maintaining a clean environment, being aware and routinely checking for signs of illness, and separating sick birds from others. Signs of illness in birds can include lack of coordination, swelling around the head, neck and eyes, lack of energy, coughing, gasping or sneezing, diarrhea or sudden death. Influenza virus in droppings from infected birds can remain infectious for several days, and can be dispersed via dust. People handling birds, equipment, or cleaning cages, should maintain good hand hygiene and not take contaminated shoes, clothing, or sick birds into their living area.

The public can participate in reducing the spread of the virus more widely by reporting sick or dead birds to the relevant agency (see: provincial and territorial contacts), avoiding direct contact with wild birds, and preventing pets from coming into contact with live or dead wild birds. The BC SPCA recently advised members of the public to remove backyard bird feeders to reduce congregation points for birds, and to reduce wild birds being exposed to bird droppings when feeding on dropped seed below feeders. Environment and Climate Change Canada has not recommended the removal of backyard feeders at this time, but suggests locating feeders away from poultry and domestic animals, and to regularly clean feeders.

Tracking the spread of the virus and additional resources:

Several websites are available to assist in tracking the number of cases in flocks and wild birds across Canada. Additional resources on avian flu and websites providing guidance for people in contact with birds are listed below:

Canadian resources

• Dashboard: Highly pathogenic avian influenza – wild birds (ECCC/CWHC/CFIA)
• Status of ongoing avian influenza response by province (CFIA)
• Map: Highly pathogenic avian influenza zones (CFIA)
• Fact sheet - avian influenza (CFIA)
• Avian biosecurity – protect poultry, prevent disease (CFIA)
• Precautions for bird banders, aviculturists and wildlife rehabilitation centres (PHAC)
• OSH Answers fact sheet: avian influenza (Canadian Centre for Occupational Health & Safety)

US and international resources

• What to know about bird flu and Frequently asked questions about avian influenza (US CDC)
• What should local health departments know about avian influenza: A Q&A with CDC (NACCHO)
• Defend the flock resource center (USDA)
• Fact sheet: Highly pathogenic avian influenza virus A(H5N1) (European Centre for Disease Prevention and Control)
• Influenza (avian and other zoonotic) (World Health Organization)

Author

Juliette O'Keeffe is an EH & KT Scientist at the NCCEH.