Infected birds transmit H5N1 to one another through nasal secretions, saliva, feces and blood. Other animals, including humans, may become infected with the virus through direct contact with avian bodily fluids or through contaminated surfaces.
Human cases of H5N1 often result from contact with infected poultry, particularly in live bird markets and farms, which are believed to be major reservoirs for the virus. Avian H5N1 however, is also carried by migratory species of birds, which further spread H5N1 to other parts of the world.
In 2004, researchers discovered that H5N1 is a more potent pathogen than originally assumed, attacking waterfowl, chickens, crows, pigeons and ducks, as well as mammals, yielding a high mortality rate. Avian flu is now considered a significant global health threat, with the very real prospect of an international pandemic, causing widespread fatality.
Indeed, the mortality rate in humans contracting H5N1 has been estimated to be around 60 percent, making it more lethal for infected individuals than Spanish influenzaa genetically similar strain that killed 50-100 million people worldwide during the pandemic of 1918.
Currently, H5N1 is not highly transmissible to humans from birds and has a very low rate of human-to-human transmission, (though around a half dozen cases have been reported). Should a small number of mutations render H5N1 more easily transmissible among humans, the conditions for a deadly pandemic will have been met.
In addition to mutations, mixed forms of influenza virusknown as reassortant strainscan occur when a single individual is infected with two versions of a given virus and they exchange genes. An H5N1 reassortant could render avian influ
|Contact: Joseph Caspermeyer|
Arizona State University