Flu (influenza) — Is It Really Just For The Birds
The historical approach which both human and veterinary medicine has used to conceptualize flu (true influenza – not just coughs and colds) is that it is an offshoot from birds. Pigs had also been identified as carriers. But the world believed that the disease was primarily a human disease and constrained to avian and porcine reservoirs. And thus the classic human — avian — porcine triad was propagated.
This classic triad dominated our philosophy and was used to describe and teach the epidemiology of influenza for nearly 20 years.
The possibility that influenza could affect our companion dogs and cats was not even entertained by scholars.
The summer of 2015 changed all of that.
When, first Chicago, and then Florida, Atlanta and eventually all of the United States erupted with a virulent canine strain of influenza.
Dogs were dying, boarding kennels, and shelters were being closed, fear gripped the canine owning population. Many (including myself) changed travel plans to shows and exhibitions and stayed home. The American Kennel Club canceled competitions.
This infection would eventually be identified as a new strain of influenza (H3N2) and was traced back through its DNA and molecular structure to avian reservoirs in Korea and parts of Asia.
The gravity of the situation was severely felt by those of us who travel with our canine companions either individually, or in groups to dog shows and competitions. And the boarding and/or doggy day-care frequent flyers who capitulated to the top of the risk pyramid.
Today our understanding of this disease has changed and will continue to change as our knowledge base evolves and the influenza virus itself continues to mutate.
The following diagram best describes our understanding today. Please do not be intimidated by the complexity of this diagram.
The takeaway is simple: influenza affects multiple species. It is a true emerging zoonosis. [Zoonosis: a disease that can be transmitted from animals to humans. – Classic example, Rabies] The avian (primarily waterfowl) reservoir is healthy and here to stay. Transmission to species that contact infected waterfowl is extremely high. Now the virus has definitely been identified in bats and the only question I have is when, not if, direct transmission will be documented between bats and people. In my humble opinion it’s only a matter of time.
With primary reservoirs in waterfowl (ducks and geese) who migrate from South America to Alaska. And from Siberia to Australia on the opposite sides of the world, this infection appears to be here to stay and will continue to erupt in people dogs, cats and multiple species for the decades to come.
Influenza is truly an emerging zoonoses — a force to be reckoned with and no longer to be taken for granted.