In 2004, the World Health Organization confirmed 11 human cases of H5N1 in Thailand and Vietnam, which resulted in eight deaths. However, no person-to-person transmission cases were identified. Vietnam also announced that the H5N1 avian flu virus had spread to many of their poultry farms. Pakistan also confirmed an outbreak of this form of the bird flu, and Indonesia discovers an outbreak of bird flu among chickens.

Later in 2004 the H5N1 virus was reported to have killed three more people in Vietnam. In November 2004, WHO warns the public that the H5N1 flu virus could spark a flu pandemic that would likely kill millions of people. In February 2005, thirteen more deadly bird flu cases occurred in Vietnam, and a report of likely person-to-person transmission is reported in the New England Journal of Medicine. Later in 2005, the European Union urges member countries to prepare for bird flu pandemic.

In November 2005, President Bush outlined a $7.1 billion strategy to prepare for possible bird flu pandemic. By the end of 2005 the death toll for the bird flu pandemic had reached 74 in Asia. By February 2006 the death toll had reached 88, with the last two deaths being reported in Indonesia. In March 2006 the UN stepped up its efforts to battle the spread of the bird flu after China reported its 10th death caused by the virus. In 2006 the bird flu had spread to many countries in Asia and Africa and Europe, including Cambodia, Egypt and Russia.