Bird flu viruses

Direct bird to human transmission works like these:

Wild birds shed the virus. Infected migratory waterfowl, the natural carries of bird flu viruses, shed the virus in their droppings, saliva and nasal secretions. The virus spreads to domesticated birds. Domestic poultry become infected from contact with these birds or with contaminated water, feed on soil. They may also catch the disease the same way human contract conventional flu by inhaling the airborne virus. Bird flu spreads quickly and lethally within a flock and is inadvertently transported from farm to farm on tractors and other equipment on cages, and on worker’s shoes and clothing. Heat destroys the virus, but it can survive for extended periods in cool temperatures.

Markets provide pathways to humans. Open air markets, where eggs and birds are often sold in crowded and unsanitary conditions, are hotbeds of infection and spread the disease into the wider community. Cock fighting, rampant through out much of Asia, has also been implicated in the spread of bird flu fighting roosters are often trucked long distances and smuggled across borders. At any point along the way, humans may pick up the virus through close contact with sick birds or contaminated surfaces. An ailing bird can shed the virus in its feathers as well as in droppings, and some people have contacted bird flu simply by touching an infected chicken or fighting roosters.

Influenza virus

The case of world wide travel has the potential to spread bird flu around the globe, although that hasn’t happened yet. Scientists don’t think that migratory birds are carrying the virus from continent to continent because outbreaks haven’t followed traditional flyways. Instead, outbreaks seem much more likely to spread locally through well markets contaminated clothing and equipment and smuggled birds.