Avian influenza is an infectious disease of birds caused by type A strains of the influenza virus.
- The disease, which was first identified in Italy more than 100 years ago, occurs worldwide.
- All birds are thought to be susceptible to infection with avian influenza, though some species are more resistant to infection than others.
- Infection causes a wide range of symptoms in birds, ranging from mild illness to a highly contagious and rapidly fatal disease resulting in severe epidemics. The latter is known as "highly pathogenic avian influenza". This form is characterised by the sudden onset of severe illness and rapid death, with a mortality that can approach 100 per cent.
- H5N1, one of more than a dozen subtypes of influenza virus which are known to infect birds.
- H5N1 is of particular concern for several reasons, including its ability to mutate and its propensity to acquire genes from viruses infecting other animal species.
- H5N1 variants first demonstrated a capacity to directly infect humans in 1997. To date more than 100 people have died as a result of infection with the virus, mainly in Asia. These have mainly been people living or working in close proximity with birds or poultry.
- Health experts maintain that unlike normal seasonal flu, where infection causes only mild respiratory symptoms in most people, the disease caused by H5N1 follows an unusually aggressive clinical course, with rapid deterioration and high fatality.
- Of even greater concern to health experts is that the virus, if given enough opportunities, could change into a form that is highly infectious for humans and obtain the ability to spread easily from person to person. Such a change could mark the start of a global pandemic. ... Martin Wall