To start the outbreak quest, you must follow the path you follow in one of the adventures (unsure which one, sorry. You can look up the path) until you reach a set of vault doors. From where you enter take the one on your left, go to the center of the control room, and the quest is collected from the object on the desk that can be interacted with. The prerequisites for the object on the desk being available are: -Completed the main quest for Titan -Spared Mithrax at the end of the quest

Google there are several reasons this could be happening the biggest one is that you have not completed the beginning adventure on Titan for it.