Avian influenza, or how it is commonly called, the bird flu, is a strain of the flue virus adapted to birds.  This means that the standard strain of influenza has been adapted to a specific, individual host, in this case, birds.

If you look further into the naming of the avian flu, you could technically say that avian flu is the influenza A virus.  This is because all the subtypes of the influenza A virus affect and are adapted to birds.  However, this does not mean that these flu strains cannot affect humans. In fact, avian influenza has led to influenza pandemics in humans, including the H1N1 flu scare a few years ago.

The way that individuals contract and spread avian flu is somewhat simple to discover.  Many of the cases of avian flu in humans are caused by two things.  Either from handling infected birds that have died from the virus or coming into contact with infected fluids from similar birds.

The most dangerous pandemics of avian flu are caused when domesticated birds are infected with a common strain of the virus like H5N1.  This is because these birds are in very close with one another and the virus can spread quite quickly.

This is a major problem in poultry farms in Asia especially because the conditions in these farms are not monitored as closely as they are in the United States; therefore, it is more likely for a pandemic to break out.  However, it is more difficult to spread the avian flu from human to human without close contact that lasts for an extended period of time.

The spread of avian influenza from Asia to Europe can actually be traced to different infrastructural devices rather than natural bird migration patterns.  For example, when birds migrated south from their breeding grounds in Asia, it did not cause a rise of infection.

However, increased infections were found along various railroad routes, roads, and Country borders.  This leads to the conclusion that poultry trade is leading to the spread of avian flu more frequently than natural migration patterns.  Poultry trade that spreads avian flu can be both legal and illegal trade.  This can be a good thing though because it can make containing breakouts easier due to knowing various shipping and trading patterns.