1. Avian Influenza is an infection caused by viruses that are found naturally among birds.
Notes: Wild birds worldwide commonly carry the viruses in their intestines or respiratory tracts but usually do not get sick from them. However, avian influenza can be contagious among birds and can make some domesticated birds - including chickens, ducks and turkeys - very sick and kill them. The risk to humans of avian influenza is generally low to because the viruses occur mainly among birds and do not easily infect humans. However, during an outbreak of avian influenza among poultry, there is a possible risk to people who have contact with infected birds or surfaces that have been contaminated with excretions from infected birds that carry the virus.
2. Avian influenza also referred to as bird flu, is a disease of birds (e.g. ducks, chickens). Between 2003 and 2006 the H5N1 avian influenza virus has infected millions of birds. Although it infected after having close contact with birds. Also see influenza, seasonal influenza, and is primarily a disease of birds a small number of people have also been pandemic influenza.
(2006, Pandemic Influenza Business Continuity Guide & Template for San Francisco Businesses. San Francisco Department of Public Health. Communicable Disease Control and Prevention Section.)
3. The bird flu—This is a virus that infects wild birds (such as ducks, gulls, and shorebirds) and domestic poultry (such as chickens, turkeys, ducks, and geese). There is flu for birds just as there is for humans, and as with people, some forms of the flu in birds are worse than others. AI viruses are classified by a combination of two groups of proteins: the hemagglutinin or H proteins, of which there are sixteen (H1-H16), and neuraminidase or N proteins, of which there are nine (N1-N9).
(2008, Geary W.Skick. Protecting your business in a pandemic : plans, tools, and advice for maintaining business continuity. ISBN: 978-0-313-34602-6)