It is not entirely certain that the "Spanish Flu" of that time was a direct "mutation" of the avian flu virus to a strain which enabled direct human to human contact of the disease. Although humans can contact "bird flu" from poultry, the virus does not seem to be generally passed on from one person to another. The Spanish Flu is thought, by some researchers, to have been a strain of avian flu which infected swine and mutated in pigs to a strain that could be passed by human to human contact, although that is not entirely certain either   Some insight here

Heric, I haven't really looked in to what has been occurring in Asia recently, regarding human to human contact. It would seem though, that the human conditions in parts of China could be considered equivalent to the crowded conditions experienced by battery raised chickens and subsequently the usual breeding ground for pandemics.

Regarding free range poultry, especially in the Fraser Valley, it would seem far more likely that free range birds, which are at a higher risk of exposure to the virus from migratory birds that winter there, would always be at greater risk, than poutry raised in an enclosed, somewhat controllable environment. So I would think that as long as you have free range poultry, you will always have the possibility of them contracting "bird flu". Ya pays yer money and ya takes yer chances.