Two more deaths have been attributed to bird flu in Vietnam, bringing the total number of deaths since December 30 to nine, officials said Saturday. A 35-year-old woman, Mai Thi Truc Ly, died Friday, one day after being transferred to the Tropical Diseases Hospital in Ho Chi Minh City and tested positive for H5N1 the same day. A 17-year-old boy, Bui Tan Tai, who died on January 15 also tested positive for bird flu Friday, said Phan Van Tu, Director of the laboratory at the Pasteur Institute in Ho Chi Minh City. The boy's 22-year-old sister is also showing signs of the illness and has been transferred to the Tropical Diseases Hospital, said Tran Le Minh, Director of Bac Lieu General Hospital. The World Health Organization has repeatedly warned that if the disease, which has a 70 per cent fatality rate, became transmissible between humans it could cause a global pandemic and kill millions of people worldwide.