Type A viruses such as the avian flu can be transmitted to more than one species in that humans as well as animals are affected. The danger to this virus is of antigenic shift because the virus and it's subtype is transmitted from one species to another (animal to human). Whereby, if the virus adapts another mutation within the human body cells thus enabling it to be spread from (human to human), the virus has created a new subtype form affecting humans. The mutation of pathogens from (human to animal) contamination would again be of antigenic shift as this new subtype of the virus could possibly erupt to affect the animal species.
If the potential of two new subsets can result from type A influenza (human to human) and (human to animal) then there needs to be a vaccine, antiviral medication for both species (human and animal) to protect against type A influenza.
Like most vaccines, in terms of prevention the actual virus may be used to prevent the spread of type A influenza strains or the formation of a completely new one. If proteins(antigens) from the contaminated birds and their nest eggs are used to create antibodies that can prevent type A influenza from occurring from (animal to human); and subsequently new strains of (human to human) and (human to animal) this may assist in preventing type A influenza worldwide. In doing so this will clip the wings of an epidemic!