We shoot at it from one end and they shoot from the other.
Influenza is a special type of zoonosis.
Most of the many strains originate in birds but bird flu is generally not transmitted directly to people. Pigs can carry both bird flu and human flu, and it is thought that most human influenza comes from birds, to pigs, then to people. The elimination of the middle man, or middle pig, as it were, opens up wider opportunity for spread to people. This further increases the potential for a significant epidemic. Most influenza viruses that infect birds do not make them sick.