AVIAN INFLUENZA'S ORIGIN
With all the news circulating about the bird flu in the past few years, you have probably heard just about everything. However, there is one question that is often overlooked: Where does avian influenza come from?
During the 1960s and 70s, new breakthroughs in technology allowed scientists to learn more about influenza than ever before. However, scientists still did not know exactly where influenza viruses came from. In 1974, after years of investigation, researchers revealed that the origin of all influenza viruses was the migratory waterfowl (i.e. wild ducks and geese.) These birds are the natural habitat for fifteen different avian influenza subtypes. Influenza viruses live inside of the birds, multiplying and flourishing inside the cells lining the bird's intestinal tract. Surprisingly, these flu viruses are mostly harmless to their hosts and the majority of bird species (except for domestic birds). Experts believe that this relationship is the result of the virus' gradual adaptation to the host over many centuries.
High concentrations of avian influenza viruses are present in the feces, saliva, and nasal secretions of the migratory waterfowl. Much of this ends up in the water supply and in turn, other birds in contact with the water become 'infected' as well, beginning the cycle once again. Avian influenza viruses flourish during the late summer, when flocks of ducks and geese around the world prepare to migrate. During migration, wild birds shed virus (low pathogenic H5 and H7 subtypes) in their feces for up to a month after infection and in turn, the virus is easily transmitted to other wild and domestic birds. After migration, influenza seemingly disappears in the fall, until the next summer, when the process begins once again.