The Infected
Your targets are humans still clinging to some semblance of life, but are antisocial to the point of reasoning. In fact, thanks to the mysterious viral outbreak, these entities (now making up the bulk of the population) are quick, ravenous beasts. They range from groups of Common Infected (the most “human” of the foes, known colloquially as “zombies” and the “undead,” despite the lack of accuracy in those descriptions) to Uncommon Infected (five main types of Common Infected that appear only in a specific Campaign and have a special ability) to and Special Infected (eight more powerful entities with particularly aggressive mutations and abilities). Let the culling commence!
Common Infected
The bulk of your killing involves dispatching these foes, which are reasonably weak singly or in groups of two or three, but a real problem when they arrive en masse in a large swarm known as a Horde.
A Horde is well over a dozen foes, with more constantly streaming in until a noise is abated, or the Survivor targets flee the area.
Common Infected are attracted to light (so Flashlights on your weapons help beckon them over, into your sights). Try having some of your team “lit up” to attract foes while others provide cross fire from safety). Common Infected also react to sounds.
These attracting sounds can be the beeping of a Pipe Bomb, a car alarm, or other noise, such as an engine sound, a hatchway opening, or some other audible noise.
These noises attract a mass of foes and usually the Horde. Back up your team by staying close to them so none of you is overwhelmed.
Common Infected also run to Boomer Bile, which is vomited by that type of Special Infected or used as projectiles after being collected in vials.
Survivor stances and weapon use affect your chances of victory. When a few Common Infected are roaming, you may want to switch from a Primary Weapon to Pistols (or the Magnum) to conserve your main weapon’s ammunition.
Headshots usually take one or two bullets to dispatch a Common Infected, no matter what the ranged weapon.
Long-range weapons, or those with good accuracy, are recommended for use when you first enter a new location and you can see a few Common Infected shuffling about. Drop them before you reach them!
Melee Weapons are extremely useful (many swear by them, and also swearing ecstatically when using them) during close combat, or after being surrounded by a Horde.
Produce your chosen implement and hack away, turning on the spot to defeat any foes behind you or to the sides.
This cannot be understated: Melee Weapons are a lifesaver during Horde swarms, or after you’re covered with Boomer Bile.
Secondary alternatives are Shotguns or other ranged weapons that have excellent short-range potential.
If you don’t want to use Melee Weapons exclusively, you can have your team stand in a number of defensive postures, such as with teammates at the front crouching (so they aren’t shot at by friendly fire), and those behind standing—all blasting away. Do this up against a wall or in a corner until the Horde threat has been defeated.
Another defensive posture is behind a narrow location that the Horde must run through. “Funneling” the enemies like this is helpful as you can blast away at a specific location (usually through multiple foes in a row with powerful firearms), place an explosive object there, or just stand and hack with a Melee Weapon and watch those zombies fall.
An example of a funneling location is the hatchway at the downed aircraft during Swamp Fever.
You can also try placing obstacles between you and the Horde. Shut doors in a room you’re in, so foes take time to bash their way in.
You can tag foes with impunity through the bars of the Safe Room doors, too. The problem with these plans is that attacks will continue indefinitely, so advance during a lull in the action.
Finally, Common Infected are used as a swarming “weapon” by Special Infected during Versus Mode.
Moving to attack enemies already engaged in a frantic fight with a Horde, picking off stragglers preoccupied with Common Infected culling, and having Common Infected swarm a foe grabbed by a Special Infected to act as “bullet sponges” are all viable plans for those playing as Infected in Versus and Scavenge modes.
Survivors should react by removing the Common Infected threats, for example, you can coat the Special Infected with a Bile Bomb (so Common Infected turn on them), or lob a Pipe Bomb to remove Common Infected from an area. This allows Survivors to challenge Special Infected more easily.
Bile Bombs, recently discovered projectiles, are very effective in many ways. When you throw them, all nearby Common Infected gather around its green gas cloud.
This makes it easy to clear areas and kill them. But the real fun comes from hitting a Special Infected with a Bile Bomb and watching the Common Infected turn on their Special brethren!
You can even throw Bile Bombs into a group of Common Infected so they attack each other!