Types Of Flu »

H5N1

The name H5N1 refers to the subtypes of surface antigens present on the virus that is hemagglutinin type 5 and neuraminidase type 1. H5N1 is a type of avian influenza virus (bird flu virus) that has mutated through antigenic drift into dozens of highly pathogenic varieties. It's a highly pathogenic strain of avian influenza .The first case of this flu appeared in China in 1996 in birds and in Hong Kong in 1997 in humans.

This infection of humans coincided with an epizootic of H5N1 influenza in Hong Kong's poultry population. This panzootic (a disease affecting animals of many species especially over a wide area outbreak was stopped by the killing of the entire domestic poultry population within the territory.

122 cases of infections in humans, resulting in 62 deaths, have been confirmed outside of China till November 1, 2005. Thirteen countries across Asia and Europe have been affected. Additionally, more than 120 million birds have died from infection or been killed to prevent further infections.

The infected birds pass on H5N1 through their saliva, nasal secretions, and feces. Other birds may pick up the virus through direct contact with these excretions or when they come in contact with surfaces contaminated with this material. Mostly migratory birds are the carriers of the H5N1 virus so it's easier for the disease to spread to all parts of the world. Past outbreaks of avian flu have often originated in crowded conditions in southeast and east Asia, where humans, pigs, and poultry live in close quarters. In these conditions a virus can mutate into a form that more easily infects humans.

The majority of H5N1 flu cases have been reported in southeast and east Asia. Once an outbreak is detected, local authorities often order a mass slaughter of birds or animals affected to prevent it from spreading. H5N1 infections in humans are generally caused by bird to human transmission of the virus. A few isolated cases of suspected human to human transmission exist, but there is no proof either way in those cases.