Saturday, May 16, 2015

The Nature of Avian Flu

Avian flu, commonly known as Bird Flu, is caused by a spectrum of influenza A viruses; many strains and subtypes have been documented and some are highly pathogenic to both wild bird and domestic poultry populations.  While past severe outbreaks of avian influenza have occurred primarily in Asia and Africa, the current North American outbreak (the first since 1983) began in December of 2014.

The spread of avian flu across the Continent is thought to result from infected migrant waterfowl though other regional carriers may be involved.  Once the virus infects individual birds at a poultry farm, it may spread quickly through the closely confined population and, potentially, to other local populations; some strains have been associated with a death rate of 90% or more.  As a result, when evidence of avian flu is documented on a poultry farm, the entire population of chickens, ducks or turkeys is culled and the facility must be disinfected.  The current outbreak is especially severe in Iowa, where more than 25 million chickens have been culled, but local or widespread infection has been documented in 16 States to date; as a result, the price of eggs, poultry meat and egg-containing products is expected to rise significantly.

While human infection from avian flu has occurred in Asia (almost exclusively in those handling infected birds), the current U.S. strains have not demonstrated the capacity to infect humans.  Human to human transmission of avian flu has been very rare but can occur with some strains under special circumstances (direct contact with infected secretions).  Nevertheless, influenza viruses mutate at a high rate and avian flu may threaten human populations in the future.