Common Infected

Common Infected, also known as The Horde are the most commonly-faced enemy and the easiest to defeat. They are completely AI-controlled and fairly weak. Their strength lies in the fact they attack in groups sometimes as large as several dozen, known as hordes. While they seem capable of ignoring pain, they can still be killed as easily as a normal human can. They are capable of climbing ladders and scaling objects.

Common Infected react violently to the pipe bomb and will ignore Survivors to investigate it instead.

Appearances and Action
Common Infected come in variety of appearances, both male and female. Some infected models can be seen in any scenario of the game, while others, such as the infected patients in Mercy Hospital are only encountered at certain areas. When not attacking, they are very vulnerable when sitting down, leaning on walls, or simply standing. They are easily provoked by light, sound, or touch, but are normally only dangerous in large groups or when completely surrounding a player. The heads, arms and legs can all be shot off, this happening easiest using a shotgun or hunting rifle. The Infected react naturally to gunfire in their vicinity, turning towards the sound to attack the shooter. Shooting one in the foot will cause a very different reaction than shooting one in the chest with a pump shotgun. They are often seen engaging in bizarre activities (e.g. vomiting, attacking inanimate objects, fighting each other) when unaware of the Survivors, but begin to rush at you when they spot you. A common infected's attack slows down the target player, meaning that it's hard to run away from a mob of them that is close to you.

Tactics
Common Infected are only strong in numbers. Sticking together is key to keeping them off of you and your teammates' backs. If you are concerned about conserving ammunition, consider using the pistol, which kills them in just a few shots or one headshot on any difficulty.

When a horde is about to attack, the best tactic is to back into a corner (preferably) or a wall. Assign the front two Survivors to crouch and melee continuously while the two Survivors behind them stand and fire their weapons at them. This works equally well when slimed by the Boomer.