Pandemic avian influenza - Essay Example

Each combination represents a different subtype. All known subtypes of influenza A viruses can be found in birds. The H5N1 subtype of the avian flu is currently causing alarm all over the world. Avian influenza viruses are carried by wild birds in their intestines, but usually do not get sick from them. Domesticated birds, including chickens, ducks, and turkeys, are very much prone to infection to avian influenza and it can affect some birds and make them very sick and even kill them. Infected birds spread influenza virus through their saliva, nasal emission, and feces.

Domesticated birds can get infected with avian influenza virus through direct contact with infected waterfowl or other infected poultry, or through contact with surfaces such as water, fowl feed, feces or cages that have been contaminated with the virus. Two main forms of disease are caused by avian influenza infection in domestic poultry that are distinguished by low and high extremes of virulence. The low pathogenic form may go undetected and usually causes only mild symptoms such as ruffled feathers and a drop in egg production.

However, the highly pathogenic form spreads more rapidly through flocks of poultry. This form may cause disease that affects multiple internal organs and has a mortality rate that can reach 90-100%, often within 48 hours. The H5N1 virus is highly pathogenic.PREVALENCEDuring 2004, large parts of Asia experienced unprecedented outbreaks of highly pathogenic avian influenza, caused by the H5N1 virus, in poultry. ETIOLOGYMost pandemics over the centuries have originated in parts of Asia where dense populations of humans live in close proximity to water fowl, ducks and pigs.

In this part of the world, surveillance for both animal influenza and clusters of unusual respiratory disease in humans performs an important early warning function.PATHOPHYSIOLOGYThe outbreaks of highly pathogenic H5N1 avian influenza in Asia in 2004 are clearly unprecedented in respect of the geographical scale and the endemicity of the virus, which now appears firmly entrenched in parts of Asia. Other unique features of the outbreaks suggest that the complex ecology of influenza viruses may be changing in ominous ways.

Domestic ducks are now known to be excreting H5N1 in its highly pathogenic form yet - like wild ducks - appear to be perfectly healthy. They may thus be silently perpetuating transmission of the virus to chickens and other poultry and possibly also to humans. The recent detection of highly pathogenic H5N1 in dead migratory birds - long considered asymptomatic carriers - may suggest another ominous change, but more research is needed before any conclusions can be reached. The factors that determine the interspecies transmission and pathogenicity of influenza