Birds and Influenza

Avian Flu Jumps from Birds to People, but Migrating Wild Birds May Not Bring it to North America

Jul 18, 2006

Influenza spreads from birds to people. When it passes from human to human efficiently, it can cause a pandemic. Domestic birds are the ones to watch with the H5N1 strain

Threat of a pandemic.

There is no disease threat today that frightens people more than the possibility of a global pandemic of avian influenza. Drug companies are scrambling to produce vaccines and antiviral drugs, while health organizations ramp up surveillance and formulate plans so they'll be ready should the worst occur. The thought of a virus easily transmissible from person to person with a fatality rate of 70 percent or higher conjures up a very different world from the one we are used to. So what is it about birds and flu?

Influenza comes from birds.

It seems that bird viruses are able to jump to humans and make us sick with unpredictable regularity. It can happen in several ways. In one scenario, a pig has an important role: the pig is the influenza mixing vessel where a virus from a bird and one from a human commingle, share some genetic code, and produce a new virus that is known as the swine flu - a nasty pathogen in humans. In a second scenario, the human is the mixing vessel: the bird virus and the human virus mix in a human to produce a new virus that becomes an epidemic or pandemic strain.

The current avian flu virus, called the H5N1 strain, is something else again. It is a bird virus that can simply infect humans and make them very sick without exchanging anything with another virus - an unusual scenario, but probably not a new one. What the virus can't do (yet) is pass easily from one human to another, thus preventing it from becoming a pandemic strain. If H5N1 mutates in such a way that it can leap from human to human, it will spread very rapidly, and it may be very dangerous (although there is no certainty that the mutated strain would behave in the same way in people as the current H5N1 virus does).

Birds carry H5N1.

They are the innocent carriers of a nasty virus that can kill them as well as us. There has been a lot of speculation about H5N1 being carried from one part of the globe to another by migrating wild birds, and this does indeed appear to be happening to some extent, but it's unknown whether it's likely to appear in North America by this route. Dr. Todd Hatchette, medical microbiologist at the Queen Elizabeth II hospital in Halifax, Nova Scotia says that it has probably not happened with other flu viruses: the viruses of North American wild birds and the birds of Europe and Asia have remained distinct in the past.

It looks as if, for now, domestic birds are the ones we need to watch, and the best advice is still "never handle a sick or dead bird without taking precautions to protect yourself."

The copyright of the article Birds and Influenza in Birds is owned by Rosemary Drisdelle. Permission to republish Birds and Influenza in print or online must be granted by the author in writing.