Figure 1

A, Large size chicken (yellow bars) and duck (green bars) farms and their respective populations of chickens (red circles) and ducks (red square) in South Korea by year are shown. B, Spatial distribution of chicken (yellow bars) and duck (green bars) farms in South Korea by province are shown. C, The number of AI outbreaks in the poultry farms in South Korea 2003 (blue bars) and 2005 (gray bars) are shown after the first outbreak. Bars represent the number of outbreaks during the specified period. The line represents the cumulative number of AI outbreaks in poultry farms in South Korea 2003 (blue circle) and 2005 (blue square). D, The number of outbreaks on poultry farms is shown by the provinces in South Korea 2003 (blue bars) and 2005 (gray bars). There is no AI outbreak in GW and JJ province due to geographical reasons. Specifically, GW province is the province farthest away from the first AI outbreak and JJ province is an island of South Korea, which can hardly or cannot be directly reached by truck transportation.