Zombies are dead people who come back to life, and those infected are living beings infected by a virus. In both cases a human can be infected by bites, scratches etc... basically by direct contact with blood.

The big difference is that infected people are also infectious through fluids. Another big difference is that to become a zombie you must die first, while becoming infected happens more immediately and while you are still alive.

The main difference is that the muscles and organs of zombies are dead, obviously. Unlike those infected, whose bodily functions are active and even enhanced, so... run!

The bottom line is that an infected person is not a zombie.