The Gellerpox is a new plague created by the Chaos God Nurgle which has arisen in the aftermath of the Great Rift's creation, and targets those who operate the Geller field generators on the Imperium's starships. Those afflicted by this disease organize into warbands of chaos mutants known as the Gellerpox Infected.
The Gellerpox first causes strange dreams among the Geller field operators, which subtly manipulates them into removing the wards of protection on the invaluable generators and deliberately sabotage their work on the machines. Once the Gellerpox infection reaches its peak, the Geller field generators and their operators are fused into a horrific union, that transforms the lower decks of starships into heaving bio-organic hellscapes, from which hordes of Mutants spill forth. As a result of the plague, Gellerpox Cults have begun springing up across the galaxy.
The transmutative power of the Gellerpox pox is not limited to just humans or organic creatures such as rodents and parasites, but rather entire ships will become corrupted alongside their crew. At the height of an infestation, the gellerpox virus opens a tiny rift in to the Warp. From this hole emerge Glitchlings.