Originally Posted by L.A. Chieffan
it's semantics really. we know that everyone turns when they die but it could be that the bite itself causes death, like poisoning the body. Which is why Herschel didn't die or turn because they cut his leg before it spread.
This. The bite causes a fatal infection that kills. Once the person dies, they turn (as does everyone in the Walking Dead world). They stopped the infection from spreading by amputating Herschel's leg, thus saving him.