Bird flu was first identified in Italy in the early 1900s. In 1960, more than 1,000 common terns died in South Africa. This was the first case of high mortality caused by avian influenza, which belonged to the H5N3 type.

According to a technical document released by the UNEP working group on the Convention on Migratory Species, the source of H5N1 avian influenza comes from intensively reared poultry. The extreme rearing environment causes the virus to mutate, and human activities such as bird trade, vaccine abuse, and transportation also It has a role in promoting the mutation of avian influenza virus. Field studies have shown that the vast majority of wild birds that suffer from avian influenza are species that have close contact with human-raised poultry during migration, wintering and breeding, while those wild birds that have been kept away from human society from beginning to end, even if they are waterfowl, and maintain high population densities, so far there have been no reports of avian influenza outbreaks.

Viruses originating from feedlots infect wild birds, especially waterfowl, allowing the virus to spread as the birds migrate. The outbreak of avian influenza in East Asia in late 2003 and early 2004 is believed to have validated the hypothesis that migratory birds spread the virus: the epidemic first appeared in southern South Korea, at a stopover for migratory birds, then passed through Hong Kong, and finally reached Vietnam. Due to the relatively good sanitation environment in Hong Kong and the previous experience in dealing with the epidemic, the disease has not caused a large-scale outbreak locally. However, Vietnam, which has a relatively poor sanitation environment, not only kills birds, but also affects humans. By the end of January 2004, nearly 20 people had died. However, ornithologists pointed out that according to the law of the Siberia-East Asia-Australia bird migration route, migratory birds have basically completed their migration from north to south as early as the end of November to the beginning of December each year. The previous radiolocation tracking research in Hong Kong also It shows that there is almost no migratory activity of birds in mid-winter. According to other observations, the wintering grounds of most waterbirds are located in the area north of 20 degrees north latitude. Only the white-browed duck and the pin-tailed duck will move to Vietnam, but their transit time is in early December. Ornithologists generally believe that in terms of time and space, the outbreak of avian influenza at the end of 2003 did not overlap with migratory bird migration. Therefore, most ornithologists do not agree with the statement that migratory birds spread the virus.

It is not only migratory birds that are accused of spreading avian influenza virus. According to the communiqué of the third session of the Conference of the States Parties to the Agreement on the Protection of Non-Eurasian Migratory Waterbirds on October 27, 2005, the way to carry and spread avian influenza virus is not only the migration of migratory birds, but also the There are livestock transportation, poultry and cage bird transportation, activities related to this industry, legal or illegal bird trade, and human traffic.

In poultry, once infected, ducks and geese have a high disease resistance and a high chance of survival after the onset of the disease. However, chickens are very sensitive to the flu virus, and once infected, not only does it spread quickly, but the infected chickens die quickly. Farmers used to call this phenomenon "chicken plague" without paying special attention to the reasons behind it or the mechanism of the disease. It wasn't until cases of bird flu that were transmitted from animals to people that people died that people began to pay attention to bird flu. At present, the main method for people to deal with avian influenza is to carry out harmless treatment such as disinfection and deep burial after mass slaughtering of infected and possibly infected poultry, so as to avoid the accumulation of virus and then affect human beings.

In the bird flu epidemics of 2004 and 2005, some media also pointed out that the bird flu virus originated from wild birds and spread to feedlots, and then to humans. It is recommended to strengthen the monitoring of migratory birds. A few radicals even advocate culling migratory birds in addition to culling poultry, but this statement has not been recognized by ornithologists. be opposed to.