The Military Pamphlet is a pamphlet developed by the Federal Disaster Response Agency (FEDRA) that describes the four stages of infection of the Cordyceps Brain Infection fungus and contain sketches of the physical effects. The pamphlet is distributed by the Military.
The Military Pamphlet is found during the second chapter, "The Quarantine Zone", in the section "20 Years Later". Once you pick up Joel's backpack upon reaching the underground tunnel, it will already be among his personal possessions.
STAGES OF INFECTION
Stage 1 [RUNNER--DO NOT LET THEM SWARM
• Cordyceps has take over the victim's motor
functions. Fast and agile. Stage 1 infected
usually travel in packs. Do not let them swarm
Stage 2 [STALKER]
• ...hide and ambush victims...check your
Stage 3 [CLICKER--CAN'T SEE]
• Completely blind, acute hearing, use
echolocation to seek out prey. Keep your
distance! Stage 3 infected are known for their
ferocious attacks and are extremely lethal.
Stage 4 [B??????]
- The fourth stage is later revealed to be the Bloater. It was torn intentionally by the game developers, so as not to ruin the surprise of encountering the first Bloater in "Bill's Town".