You play too many video games.
Zombies are the walking dead. They die then rise from the grave(or morgue, bottom of the ocean, etc.) as zombies. This isn't 28 Days Later.
And why are we talking about zombies, "as a matter of fact," anyway?
1) If you knew how the brain works, once the heart is done, the brain is done too. Without the heart(which cannot be restarted by a virus / bacteria / chemicals / electricity), the brain cannot get blood. No heart means no lungs, that means no air, which means the brain will be 100% empty in minutes. Even if it did start again, hearing, vision, feeling, and all sensory nerves would be eradicated.
2) 28 Days Later is based off of a virus. That is logical.
3) Can't you read? The topic title is about zombies which is why we are talking about zombies.