How is avian influenza transmitted?
Avian influenza is most often spread by direct contact between infected birds and healthy birds. It may also be spread indirectly through contact with contaminated equipment and biological secretions and/or excretions. The avian influenza virus is found in secretions from the nares (nostrils), mouth, and eyes of infected birds and is also excreted in their droppings (excreta). Contact with contaminated droppings is the most common means of bird-to-bird transmission, although airborne secretions are another important means of transmission, especially within poultry houses. Droppings from wild ducks can introduce avian influenza into domestic flocks raised on range or in open flight pens.
The spread of avian influenza between poultry facilities almost always results from the movement of infected birds or contaminated people and equipment (including clothing, boots, and vehicles). Although more pathogenic strains of avian influenza virus can completely suppress egg production,the less pathogenic strains ofthe virus can be found on the inner and outer surfaces of egg shells; however, this has never resulted in hatchery transmission. Airborne transmission of avian influenza virus from farm to farm is highly unlikely because the virus cannot travel long distances through the air and it is susceptible to the effects of sun light and drying.
Influenza viruses that are considered to be highly pathogenic avian influenza can be spread from birds to people as a result of extensive direct contact with infected birds, such as during home slaughter ordefeathering of infected poultry. Public health concerns center around the potential for the virus to mutate or combine with other influenza viruses to a form a new strain that could easily spread from person to person.