"Un-gluer", The Descolada is a superintelligent virus that has infected all of the inhabitants of Lusitania. The pequeninos (piggies) cannot live without it, and life alien to Lusitania is threatened to be wiped out. The original virus rips, or "unglues" - as the name suggests - DNA strands. The strand attempts to repair itself, but its proteins are scrambled in the attempt. Death is the end result for the infected host, either resulting from the immune system's rejection of or the physical ripping apart of the body. It changes human DNA, flesh falls off, extra limbs grow onto parts of us where there shouldn't be limbs, "a new limb, not arm or leg, growing out of her hip, while the flesh sloughed off her feet and head, baring the bone" (1.32)
The engineers of the Descolada virus - the "Descoladores" - were discovered to probably be an intelligent alien race, though no meaningful contact with them has yet been made by the end of the book series. Their exact motivations or intentions are also unclear. Attempts to contact them were responded to with instructions for making chemicals that affect the same parts of the brain as heroin. Learning from the disastrous first contact with the Formics, however, it is warned not to jump to the conclusion that their intentions are negative. While clearly they possess great knowledge of biochemistry, its not clear if they were trying to enslave other races, or if this was simply their way of attempting communication.