Breaking Quarantine is a story in the Halo Graphic Novel, depicting Sergeant Johnson's escape from the Flood. Illustrated by Tsutomo Nihei.
Summary
Following contact with the Flood, Sergeant Johnson through some miracle managed to avoid being overwhelmed by Infection Forms. He fired at an Infection form which had latched onto a fellow Marine (presumably Private Mendoza), killing the Flood. He watched as the Marine transformed before his eyes into a monstrous form (what we know as Combat Forms). He took a blow to his arm from the Flood's tentacles and was thrown out of the containment room, across a large observation chamber and into the wall.
Several infected Marines started to approach him and he made a run for it, into a hallway. He locked the door with a spoofer and proceeded down the hallway. An infected Marine fired a shotgun shell that hit the wall, missing the sergeant by inches. The sergeant dove below, unloading the last remaining rounds in his Assault Rifle onto the infected soldier. He grabbed his Pistol and shot down the combat form. He made his way across the Energy Bridge, in hot pusuit, throwing a Grenade behind him, killing his pursuers. He stepped onto the lift, glad to finally escape the Flood.