Hyperevolutionary virus

The zerg hyper-evolutionary virus is an infectious disease through which infestation of living organisms is carried out. Terrans, dogs and even the organic components of adjutants are susceptible to its effects whilst the protoss are (mostly) immune.

The virus mutates extremely rapidly, making the possibility of a cure seemingly impossible. It can be spread through water. The protoss were able to devise a nano-tech serum that could reverse the effects of infestation, but this was apparently no longer viable by the Second Great War. The Swarm developed a particularly virulent strain of the virus, which renders those infected vulnerable to UV radiation.

Protoss are (usually) protected from infestation by the fortitude of the Khala, but it has failed in at least one unusual circumstance. Terrans are not as fortunate; their psionic potential was noticed by the zerg and the virus was used as a means to an end to assimilate it. The Queen of Blades was an example of a successful infestation, but most terrans, even psychics, were rendered mindless drones by the process due to genetic incompatibility with the virus. Kerrigan made efforts to remedy this and succeeded in the infestation of Ethan Stewart.

Extreme mutation by the virus will turn a terran into an aberration.