What is Bird Flu?

WHAT IS BIRD FLU and Avian Influenza?

* Avian influenza is an infectious disease of birds caused by 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 than others.

* Infection causes a wide spectrum 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 characterized by sudden onset, severe illness, and rapid death, with a mortality that can approach 100 percent.

* Fifteen sub-types of influenza virus are known to infect birds, thus providing an extensive reservoir of influenza viruses potentially circulating in bird populations.

IS BIRD FLU HARMFUL TO HUMANS?

* Human fatalities from avian influenza were unknown before 1997, when six people in Hong Kong died after being infected with the H5N1 strain of the disease.

But the destruction of Hong Kong's entire poultry population -- around 1.5 million birds -- within three days, reduced opportunities for further direct transmission to humans, and may have averted a pandemic.

* In April 2003, a Dutch veterinarian who had been working on a farm infected with bird flu became ill with an H7 strain of the disease and died of pneumonia. The vet did not take medication against avian and human flu.

HUMAN CASUALTIES FROM BIRD FLU

* 42 Vietnamese have died since late 2003. The disease has also killed 13 Thais, 7 Indonesians, 4 Cambodians and two Chinese.

COULD BIRD FLU BECOME A HUMAN EPIDEMIC?

* Although avian flu is very infectious in birds, it does not spread easily among humans. There is a danger, however, that an avian virus mixes with a human one and forms a new disease.

* The new virus could share genetic material from both viruses, being highly infectious like human flu and dangerously fatal like the avian variety.

* According to a WHO report earlier in May, the spate of human bird flu cases in Vietnam this year suggested the deadly virus may be mutating in ways that are making it more capable of being passed between humans.

-- The finding points to the greatest fear of health experts that the H5N1 virus could unleash a pandemic and kill millions around the globe if ever it gained the ability to be transmitted among humans efficiently