"Their eyes? They were as as red as a fine wine."
Once bitten by a Red Strain, a Survivor will only have a couple of hours to find an Antigen (Red Strain) before the infection sets in and they die. If death occurs, the Survivor will reanimate into a Red Strain.
The Red Strain appeared soon after the Blue Strain antigen was manufactured. It tore through military camps and shelters, destroying the last hopes that anyone had for life coming back to normal again.