[1] The H5N1 strain is a fast-mutating, highly pathogenic avian influenza virus (HPAI) found in multiple bird species.

Countries that have reported one or more major highly pathogenic H5N1 outbreaks in birds (causing at least thousands but in some cases millions of dead birds) are (in order of first outbreak occurrence): South Korea, Vietnam, Japan, Thailand, Cambodia, Laos, Indonesia, China, Malaysia, Russia, Kazakhstan, Mongolia, Turkey, Romania, Croatia, Ukraine, Cyprus, Iraq, Nigeria, Egypt, India, France, Niger, Bosnia, Azerbaijan, Albania, Cameroon, Myanmar, Afghanistan, Israel, Pakistan, Jordan, Burkina Faso, Germany, Sudan, Ivory Coast, Djibouti, Hungary, United Kingdom, Kuwait, Bangladesh, Saudi Arabia, Ghana, Czech Republic, Togo, Nepal, Bhutan, the Philippines, and Chile.

[2] Highly pathogenic H5N1 has been found in birds in the wild in numerous other countries: Austria, Bulgaria, Denmark, Greece, Iran, Italy, Poland, Serbia and Montenegro, Slovakia, Slovenia, Spain, Sweden, Switzerland, and Uruguay.

[3] Surveillance of H5N1 in humans, poultry, wild birds, cats and other animals remains very weak in many parts of Asia and Africa.

The presence of highly pathogenic (deadly) H5N1 around the world in both birds in the wild (swans, magpies, ducks, geese, pigeons, eagles, etc.)

[...] From 1997 to May 2005, H5N1 viruses were largely confined to Southeast Asia, but after they had infected wild birds in Qinghai Lake, China, they rapidly spread westward.

In January 2004 a major new outbreak of H5N1 surfaced in Vietnam and Thailand's poultry industry, and within weeks spread to ten countries and regions in Asia, including Indonesia, South Korea, Japan and China.

In October 2004 researchers discovered H5N1 is far more dangerous than previously believed because waterfowl, especially ducks, were directly spreading the highly pathogenic strain of H5N1 to chickens, crows, pigeons, and other birds and that it was increasing its ability to infect mammals as well.

[citation needed] Variants have been found in a number of domestic cats, leopards, and tigers in Thailand, with high lethality.

"[21] The initial OIE report reads: "the clinical manifestations began on 11 October 2004 with weakness, lethargy, respiratory distress, and high fever (about 41-42 degrees Celsius).

"[22] In January 2005 an outbreak of avian influenza affected thirty three out of sixty four cities and provinces in Vietnam, leading to the forced killing of nearly 1.2 million poultry.

David Nabarro later stated that as the virus had spread to migratory birds, an outbreak could start in Africa or the Middle East.

[citation needed] In 2005, it was discovered that H5N1 "could be infecting up to half of the pig population in some areas of Indonesia, but without causing symptoms [...] Chairul Nidom, a virologist at Airlangga University's tropical disease center in Surabaya, Java, was conducting independent research earlier this year.

He tested the blood of 10 apparently healthy pigs housed near poultry farms in western Java where avian flu had broken out, Nature reported.

"[23] In January, Japan, Hungary, Russia, and the United Kingdom joined the list of nations seeing a resurgence of bird deaths due to H5N1.

A purposely mutated strain [51] in ferrets[48] has engendered a notable international policy debate regarding the openness of scientific research, the mandates of public health, and the potential for bioterrorism.