Pathogenesis of Avian Influenza

Birds are infected via the upper respiratory tract, the conjunctiva or the digestive tract. Viral replication takes place in the epithelium.

Spread

• Avian influenza virus is shed from respiratory tract, conjunctiva and faeces.
• Spread can be rapid due to excretion of high quantities of the virus in the faeces. 
• Ducks can excrete virus for more than 30 days

Incubation period

The incubation period is very variable, a few hours to 18 days.

It is dependent on:

• the pathogenicity of the virus
• dose of the virus
• route of exposure
• the species infected
• the ability to detect clinical signs