Migratory Birds and Influenza

Some parts of Alaska are said to have lost more than half their population during the great influenza pandemic (worldwide epidemic) of 1918-19. At least 20 million people died as three waves of flu swept around the globe. Twenty-five million people in the United States, a fourth of the population, became clinical flu cases in the fall and winter of 1918. Of these, a half-million died.

Just why there are sudden worldwide outbreaks of influenza is not yet fully understood. But now it is known that similar flu viruses inhabit humans, horses, swine and some birds. Outbreaks of the disease have occurred almost simultaneously in humans and horses. In early 1976 an outbreak of flu at Fort Dix, New Jersey, was traced to viruses in swine.

An article in the December 1977 issue of Scientific American by Martin M. Kaplan and Robert G. Webster suggests the possibility that the virus is rapidly carried around the world by birds. Migrating mallard ducks have been found to carry influenza virus along the Mississippi flyway and through central Canada.

Influenza viruses may be carried through the region of the Pacific Ocean by shearwaters (genus Puffinus). Viruses deposited in cold waters of the Pacific Ocean off Alaska may survive for several weeks. Animals, ducks, arctic terns or other birds may pick up the flu viruses from the water and carry them along Alaska's coastal waters or inland.

Thus it seems likely that a huge reservoir of various kinds of influenza virus may be harbored in the world's bird and animal population. From time to time these viruses evolve new strains or combine in ways that make them virulent. When this happens, new vaccines to counteract the virulent strains can be quickly developed, and it is unlikely that future epidemics will equal the horrors of 1918-19.