A five-year-old boy from central Vietnam has become the latest person to contract the bird flu virus that has killed at least 46 people in the region.

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.

Some information for this report provided by AP, Reuters.