A top official of the World Health Organization told delegates at the opening of a three-day conference in Vietnam that the world is in "the gravest possible danger" of a deadly bird flu pandemic.

Dr. Shigeru Omi, the director's of WHO's western Pacific division, says the health impact of a bird flu pandemic will be much greater than that of the outbreak of Severe Acute Respiratory Syndrome.

Health experts from several nations are attending the conference in Ho Chi Minh City near the Mekong Delta, where the latest bird flu outbreaks in Vietnam have occurred. Many health experts are warning that bird flu could combine with a human influenza virus to create a disease that spreads easily among humans.