Bird Flu: How Are Americans Going to Catch It?

Bird flu, which is the lay term for the H5N1 variety of avian influenza, started in Hong Kong in 1997. Since then it has spread to China, Thailand, Cambodia, Vietnam, South Korea, Japan, Taiwan, Laos, Russia, Indonesia, Mongolia, Kazakhstan, Malaysia, Romania, England, Croatia, Macedonia, Kuwait, and most recently to Turkey.

The H5N1 virus has infected many species including ducks, chickens, turkeys, tree sparrows, peregrine falcons, great black-headed gulls, brown-headed gulls, gray herons, Canada geese, bar-headed geese, little egrets, pigs, clouded leopards, white tigers, mice, domestic cats, crows, magpies, peacocks, blue pheasants, rare eagles, turtledoves, swans, terns, and others.

Human infections have occurred in Thailand, Cambodia, Vietnam, China, Indonesia, and now Turkey. Almost all human infections have occurred by humans ingesting blood or insufficiently cooked meat from birds infected with the virus, or being in close contact with sick birds–children playing with sick or dead birds for example.

One recent case involved a person acquiring bird flu by coming into contact with a glove from a person culling (removing and killing) infected birds. There have been several instances where transmission of the H5N1 virus is thought to have occurred directly from human-to-human–parents taking care of their children who had the virus.

Transmission of the H5N1 (bird-flu) virus to humans to this point has, therefore–in the vast majority of cases–involved ingestion of, or being in close contact with, infected birds. As the virus continues to spread, via migratory birds from country-to-country, it could come to North American and the United States via this mechanism as well. If that were the case, then American’s could well be exposed to the virus through ingestion of, or close contact with, infected birds. This mode of transmission could also take place once the pandemic begins.

However, once the pandemic actually begins, by definition human-to-human transmission will be the primary mode of transmission. In other words, once the pandemic starts, those who become infected will most likely have gotten their infection from someone else–another human. And, given what we know about seasonal influenza and its transmission, it is most likely that children will be the biggest source of infection. Therefore, while we might have to worry about acquiring the virus from both wild and domestic birds, the much more important source of human infections will be each other.

Once the global pandemic starts, it will come to the United States through travelers from other countries where the pandemic has already begun–unless the pandemic actually starts in the United States–which is possible but unlikely.