Las Plagas is a genetically engineered parasite created by the Umbrella Corporation in Resident Evil: Retribution. Developed at the Umbrella Prime facility in Siberia, this parasite functioned as a performance enhancer, increasing the physical strength and healing capabilities of regular humans. It could also be implanted into Undead humans; while it didn't increase the physical strength of the Undead, it did make them more intelligent and eliminated their hunger for living flesh, making them susceptible to control.
When a group of anti-Umbrella rebels invaded Umbrella Prime, the Red Queen activated several squads of Plaga Undead to eliminate them The Plaga Undead demonstrated an ability to use weapons and tools and even drive vehicles such as motorcycles. As the rebels made their escape from the facility, they were confronted by Bad Rain, a clone of deceased Umbrella commando Rain Ocampo. Bad Rain injected herself with a Las Plagas parasite, then fought against Alice and Leon Kennedy's team. The parasite granted her increased strength and durability, and any wounds she sustained were quickly knit closed by the Plaga. However, even the Plaga could not save Bad Rain when she was plunged into the frigid Russian waters which, by then, were swarming with Undead which preyed upon her.