News - Reuters AlertNet - FACTBOX: Bird flu threatens to become global pandemic

The World Health Organisation (WHO) has issued a series of warnings about an outbreak of a deadly bird flu virus in Asia. Since 2003, the H5N1 avian flu virus has killed dozens of people in Asia and spread from Korea as far as Europe, despite attempts to contain the virus by culling millions of birds.

But what worries health experts is the possibility that the H5N1 avian flu virus will combine with a human flu virus and trigger a global flu pandemic. The WHO has warned that if this happens, the world would have just weeks to contain the virus before it spreads, possibly killing millions of people.

Following are key facts about H5N1 avian flu virus:

H5N1 is considered the biggest direct disease threat to humanity. All influenza viruses change quickly, which is why the standard flu vaccine must be changed every year. But H5N1 is particularly good at changing. The fear is it would acquire a key gene from a flu virus that already easily infects humans and become a highly contagious and deadly strain.

The WHO predicts that in the best case scenario, between two and 7.4 million people could die if H5N1 acquires the ability to spread from person to person easily. In the worst case scenario as many as 150 million people could die.

The WHO says the only possibility of containing the virus is to inoculate between 300,000 and one million people with anti-virals as soon as the pandemic is detected. However anti-viral stocks are limited ? the WHO will receive one million doses by the end of 2005 and a further two million by mid-2006.

The H5N1 avian flu virus is one of 15 known subtypes of bird disease caused by type-A strains of influenza. Type-A avian influenzas were first identified in Italy more than a century ago.

The H5N1 strain made the first known jump to humans during an outbreak in Hong Kong in 1997, which caused the death or destruction of 1.5 million birds. Eighteen people became sick and six died. It re-emerged in South Korea in 2003.

By mid-October 2005 it had been found in birds in Cambodia, China, Greece, Indonesia, Japan, Kazakhstan, Korea, Laos, Malaysia, Mongolia, Romania, Russia, Taiwan, Thailand and Vietnam.

Birds that survive infection with H5N1 excrete the virus for at least 10 days, orally and in faeces, making it highly likely to spread. Migratory birds, usually wild ducks, are the natural "reservoir" of avian influenza viruses, and usually do not become sick when infected. Domestic poultry, including chickens and turkeys, die quickly when infected.

Several companies are working on an H5N1 vaccine. The ordinary flu vaccine does not protect against avian flu.

Two anti-viral drugs can help against the infection and may even prevent it if taken at precisely the right time. They are not vaccines, but they can help to reduce flu symptoms and the risk of an infected person passing flu on to others. These are Tamiflu, known generically as oseltamivir, and Relenza, known generically as zanamivir.

Sources: World Health Organisation, Reuters

Reuters AlertNet - FACTBOX: Bird flu threatens to become global pandemic