avian influenza, H5N1

Identified for the first time in Italy in the 1900s, avian influenza is a highly contagious viral disease affecting birds that is likely to provoke an extremely high death rate (particularly among poultry, turkeys, chickens and hens).
Avian influenza also integrates strains of low pathogenicity, for which infected birds present only mild symptoms or no clinical signs at all.
It is mainly caused by two viral sub-types, H5 and H7.

Certain species of bird are more resistant than others. Ducks, for example, may be infected by pathogenic strains but only present very subtle clinical signs.
Some viruses isolated in birds are likely to infect pigs, horses or humans, but on a much rarer basis.

Don't confuse the two!

Avian influenza is subject to very specific semantics, often used incorrectly.

Avian influenza: Viral disease affecting birds which may spread to other species in a sporadic manner. It is also called avian flu.

Bird flu: Generic term used by the media referring to avian influenza and the spread of this virus to humans or other species. This scientifically inappropriate term has nevertheless slipped into everyday use to mean avian influenza.

Transmission means

The virus is spread mainly through direct (respiratory secretions and faecal matter of infected animals) or indirect contamination (exposure to contaminated matter: contaminated food, water, material or clothing).
The incubation period of the disease is three to five days. The main signs to observe in poultry are: loss of appetite, considerable reduction in egg production and especially for serious forms, digestive, respiratory or nervous symptoms which lead very quickly to death.

Influenza viruses are very prone to genetic modification, changes which may result in the emergence of a new combination against which the immune defences of the host (animal or human) present no protection.

October 2007