Poultry existed in the context of farms, markets, slaughterhouses, and roads while humans were indirectly the primary transmitters of avian flu, placing the burden of disease control on people.
The virus is spread by contact between healthy and unhealthy birds.
The main source of infection is migratory waterfowl, such as ducks and geese.
Other kinds of influenza, namely H1 and H3, are the ones that usually cause outbreaks in humans.
While several environmental, behavioral, and biological explanations for this pattern have been proposed, as yet, the reason is unknown.
This culling method was indiscriminate as a large proportion of the poultry inside these areas were small backyard flocks which did not travel great enough distances to carry infection to adjacent villages without human effort and may have not been infected at all.