A Cambodian woman has died of bird flu, becoming the first confirmed victim infected outside Vietnam in an outbreak that has killed 13 people in the past month.

A man whose brothers contracted bird flu has tested positive for the deadly virus, Vietnam’s state-controlled media reported today, as the World Health Organisation said it was investigating the possibility that one of the siblings passed the disease to another.

Vietnam today confirmed the country’s fourth death from bird flu in two weeks, as the World Health Organisation called the disease a “frightening virus” and urged stronger measures to combat its spread.