On 4 April 2023, Canadian media reported that a dog in Oshawa, Ontario, died due to an infection caused by a strain of avian influenza virus (bird flu) known as H5N1. The dog acquired the virus after chewing on an infected dead wild goose. There are no reports of transmission to humans at this time and the risk for any spread is extremely low.
Wild birds and poultry (ducks, geese, turkeys and others) in many parts of the world are carriers of many different strains of avian influenza viruses. The roughly 16 different strains are numbered based on the two proteins found on the surface of the strain. Some are deadly for the infected birds, while others are not. In 2023, at least 24 countries, including the United States, France, Belgium, the Netherlands and Italy, have reported avian flu outbreaks in domestic birds.
Potential Hazards from Avian Influenza
There are two major problems associated with avian influenza. Wild birds can infect commercial flocks of chickens and other domesticated birds. The economic consequences are serious since the entire infected flock must be destroyed to contain and stop the virus. It may involve the euthanasia of thousands of birds whenever an outbreak is detected.
The second problem involves the transmission of the virus from infected commercial flocks to humans who work in the infected environment around the flock. Even some farmers with small backyard flocks of chickens, ducks or geese may be infected through close contact with one of the infected birds. It is a rare event. During the past 25 years, a total of approximately 800 human cases of avian influenza A(H5N1) were reported worldwide, mostly occurring in Africa and Asia. Recently, one death due to bird flu was reported in Cambodia.
Although some human deaths have been reported due to unusual strains, this is rare, and to date, there are no reports of sustained human-to-human transmission. Wherever there is a report of a human case, public health and animal health authorities conduct intensive surveillance to detect any possible human-to-human transmission.
There is always a potential problem with avian influenza. If there is co-infection in the host animal with two different strains, the genetic material of the two viruses might combine to create a strain that does transmit between humans (through virus multiplication).
Such a hypothetical strain could then initiate a global pandemic. For this reason, there are various global animal and bird surveillance systems to detect any unusual events at the earliest possible time.
In summary, the risk for domestic poultry is significant. So far the various strains that have occasionally infected humans have not adapted to human infection. In the absence of documented human-to-human spread, the risk to the health of the public remains extremely low.
What’s the ultimate conclusion here? Do we need to worry? Why or why not?