Fighting bird flu

From what I understand about the theory of evolution, is that the strongest will survive. And germs like us, are growing stronger each day thanks to our stronger antibotics. They have a strong will to evolve in order to kill the next man, mammals or beasts.

So what I cant understand is that how could culling hundreds of birds prevent the spread of the bird flu. If the stronger birds do not survive to pass on their better genetic material to the next generation, how could they survive as a species.

Imagine in a chicken farm, the evil bad-ass flu sneaks in and attack a couple of birds. A couple of them survive the virus and live on. However as a safety measure, the farmer kills all the birds. Thereby stopping the virus and also the possible naturally immune cure.

Sighs... I guess in the next few generations, our great great grandchildren will have to take mulitple jabs of injections to protect them. They wont be safe within 1 hr of breathing the earth air.