Outbreak

Outbreak is a StarCraft II: Wings of Liberty mission.

Raynor's Raiders escorted the Agrian colonists to Meinhoff, but discovered an area infested by zerg. During the day the infested terrans did not venture far from their lairs and could be destroyed easily. However, during the night the infested emerged in large numbers and aggressively attacked the Raiders' base.

The enemies include infested terrans, infested marines and aberrations.

The Refugee Crisis
On the outbreak of the Second Great War, the Terran Dominion withdrew its forces to the Core Worlds. The Fringe Worlds consequently became easy targets for the invading zerg, and the colonists fled for the safety of the Core Worlds. Meinhoff, a Kel-Morian Combine world, became a staging point for the refugees. Without Dominion aid conditions in the camps deteriorated.

The refugees from Agria arrived on Meinhoff just as a zerg infestation virus was sweeping through the dense camps. Doctor Ariel Hanson appealed to Raynor's Raiders to halt the plague and save the refugees. Jim Raynor agreed, grimly noting the only way to stop it was to "burn it out." the task was made easier by the infested terrans' relative inactivity during daytime; the virus made them vulnerable to the high UV output of the local star.

Aftermath
The infested and their nests were purged and the virus contained for the time being. The Agrians departed Meinhoff in search of a safer place to settle. They eventually found Haven. On Raynor's advice, Hanson started looking for a cure to the virus.

The Kel-Morian Combine drew criticism for the deaths of so many refugees. The Combine denied responsibility.

Gameplay
The mission is divided into day and night phases. During the day, no enemy attacks on the base occur; this is the easiest time to sally out and destroy infested structures. This changes when night falls when the base comes under attack by hordes of infested terrans. During the first night, only s attack. After the second, infested marines join them. Finally, aberrations appear from the third night onward. Attacking infested structures during the night requires more care and attention, but allows the mission to be finished faster and achievements to be earned. On harder difficulties and the longer the mission takes, the more infested come out until, eventually, even a couple of buildings can still provide a constant stream of enemies. The length of the day phase also shrinks on harder difficulties, being 5 minutes on normal and 3 minutes on brutal.

The base is in the center of the map and has three entrances. The top right and bottom right entrances are initially open but are covered by a sensor tower. The bottom left entrance is initially blocked by destructible rock, and will be opened by the infested after several nights. Bunkers with s work well to hold the entrances.

The two infestors burrow during the day. If the mission is played early in the campaign and no mobile detectors are available, the infestors may be killed during the night when they surface. They are most easily killed when their surroundings have been cleared during the day; only a few marines is required to take them down.