I'm just a regular guy who is aware that in any point in time, there's a possibility of a zombie attack... Which would most likely be because of a government experiment...

No matter how the virus or parasite was created, an infected person that becomes a zombie will go through stages.

1- A newly infected person still has a complete and functioning body, minus rational thinking. Zombies will probably be able to run and move quickly, but average human behavior will be replaced with violent and swift insanity.

2- After the body dies, which would be because it isn't getting any nutrients or any of the things that an animal needs to live, it will start to decay at the rate of any average dead body. This means that the body and all that it is composed of will slowly die, including muscle tissue, which will result in slower zombies as time goes by.

3- Towards the end, zombies will most likely be almost completely harmless. They will have hardly any muscle and no energy to keep them going. The virus will most likely die soon after, resulting in a finally dead zombie.

I really hope I'm wrong though, because if any threat as serious as a zombie were to come about, I hope they won't be able to run. We would have no chance. Not even for the athletes. I try to keep in good shape myself, making sure I get my exercise and maintain a healthy diet, but I don't think I'd be able to last against a zombie of that type... Unfortunately.