The boy was was admitted to a hospital in central Vietnam early this week and tested positive for the H5N1 strain of the virus.  His 13-year-old sister died last week after suffering the same symptoms, but was not tested.

Since late December, 25 people have contracted bird flu in Vietnam, 13 of whom have died.  A Cambodian woman also died of bird flu in a hospital in southern Vietnam.

The World Health Organization is worried that the virus spread by poultry could mutate into a form transmitted easily between humans and kill millions of people worldwide.