The Infected (known as "fast zombies" in some circles) aren't zombies in the truest sense, and many (but not all) fans of Zombie fiction feel that the distinction is very important. Infected are people, technically still alive, whose bodies are ravaged with some sort of biological pathogen that irrevocably (and fatally) transforms the hosts bodies and minds. The immediate change is a total reversion to an aggressive, feral personality type. An infected will attack any human (regardless of past emotional connection) with rabid ferocity, and all the strength - and mobility - they can muster. The infected demeanor is notably hostile, hateful, and enraged. Both the biological infection, and its primal hosts spread quicker than their literary cousins, the Zombies. However Infected have been universally portrayed as more fragile, with a average life span of only weeks or months (as the body begins to dehydrate, muscles and other organs begin to fail), and can be killed by wounds to the torso, or bleeding out through extremities, whereas Zombies almost universally require their brain to be destroyed before final death, and can persist intact for years without food, water, or even oxygen.
Zombies are slow which makes escaping from a small number of them easier (although because of the Zombie's durability, their hordes tend to be greater in number). Infected are fast and very agile and will not give up chase until the target is unreachable. Both creatures seem to sense neither pain nor fatigue, and as such, will continue a foot pursuit longer than any human, so long as no complex barriers impede them or they are not yet put down for good.
Zombies are only killed by destroying the brain. Infected can be brought down by shooting the torso or any other vital body part. They can also be brought down with poisonous gas, and any other means that are fatal to uninfected humans.
Zombies do not need food so they do not starve but will decompose after a certain amount of time (not destroying them, their bodies just become weaker) This process is much longer than most decomposing corpses, as normally other organisms exist in the breakdown of tissue, but Solanum infested tissue prevents this. Infected, on the other hand, need food or they will starve and die of hunger or thirst (though the Rage virus apparently causes its hosts to become disinterested in self-nourishment, making starvation virtually inevitable).
Zombies' primary motivation seems to be the consumption of their prey (even if they do not receive sustinance from the act of consumption). Infected are motivated more on the destruction or infection of their prey, with biting being only one method of accomplishing their goal. Despite being less orally fixated creatures, the Infected are still more than adequete at spreading the disease whenever they pierce the flesh of, or project bodily fluids into the face of their prey.
Zombies are officially deceased - walking corpses that can move without dependence on oxygen on any level. Some zombies (such as Brooks Zombies) are even immune to bacteria and parasites involved in natural decomposition, and resistant to saltwater corrosion. As such, they can infest even the depths of the ocean floor. Infected are still living and breathing human beings who require oxygen, and can drown, or even die from a severely damaged trachea.
Zombies rarely reanimate in under a few hours after exposure or death. Once a host is infected with Rage, they succumb to it and become an Infected in 3-4 hours this can also take longer but no longer than five hours