Feb 26 - The World Health Organisation (WHO) confirmed on Tuesday the death of a 44-year-old Chinese woman from the H5N1 strain of bird flu.

A 23-year-old woman teacher in northern Vietnam was also reported to have died of the disease.

The outbreak of highly pathogenic H5N1 avian flu began in Asia in 2003. Following are some facts about the virus and its spread:

* Since the virus re-emerged in Asia, outbreaks have been confirmed in about 60 countries and territories, according to data from the World Organisation for Animal Health.

* The virus has killed 234 people since 2003, according to the WHO. Countries with confirmed human deaths are: Azerbaijan, Cambodia, China, Egypt, Indonesia, Iraq, Laos, Nigeria, Pakistan, Thailand, Turkey and Vietnam. Djibouti and Myanmar have had human cases but no deaths.

* The virus is known to have infected 368 people since 2003, the WHO says. Many of the dead are children and young adults.

* The WHO says Vietnam and Indonesia have the highest number of cases, accounting for 156 deaths.

* The H5N1 virus is not new to science and was responsible for an outbreak of avian influenza in Scotland in 1959.

* H5N1 is not the only bird flu virus. There are numerous strains. For example, an outbreak in 2003 of the H7N7 bird flu virus in the Netherlands led to the destruction of more than 30 million birds, about a third of the country's poultry stock. About 2.7 million were destroyed in Belgium and about 400,000 in Germany. In the Netherlands, 89 people were infected with the H7N7 virus, of whom one -- a veterinarian -- died.

* The H5N1 virus made the first known jump to humans in Hong Kong in 1997, infecting 18 people and killing six of them. The government ordered the immediate slaughter of the territory's poultry flock, ending the outbreak.

* Signs of bird flu in humans range from typical influenza-like symptoms, such as fever, coughing, sore throat and aching muscles, to eye inflammations, pneumonia, breathing problems, viral pneumonia and other complications. (Sources: OIE, WHO, Centers for Disease Control and Prevention) (Writing by David Cutler, London Editorial Reference Unit)

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