Leech

Leeches are stubby Special Infected which spew Acid onto the player or onto the ground. The Acid puddles cause continuous damage to the player if moved through or touched. The puddles evaporate after about 5-10 seconds after they first appear. If suffering from Acid damage, use the Rush action (L2) to stop the continuing damage, the same as with being on fire.

Leeches often come in groups and are somewhat weak and slow. They can be dealt with using any ranged weapon (the Flamethrower seems particularly appropriate). Meleeing them is not advisable. Upon death, they leave behind a bigger puddle of Acid which can be quite problematic, especially in tight areas.

Leeches lack direct attacks, so they do not pose much of a threat until they spew Acid. However they are the only enemy in the game that possesses any kind of ranged attack, and the only enemy with an "area denial" weapon, so they may require a slight adjustment to your tactics.

First appearance: Morrow Hospital

Trivia

 * These are a reference to Spitters from the famous Left 4 Dead 2 zombie game, as they leave acid when dead and leave puddles of acid where they spew.
 * It's speculated they are named "Leech" for the damage you take for touching the acid puddle as you would take slow damage for a few seconds.