[Name] Uroboros [Source] Resident Evil 5 [Symptoms] 
An advanced strain of the Progenitor virus, the Uroboros virus was created by Albert Wesker, with inadvertent help from Jill Valentine. Exposure to Uroboros can lead to one of two things – forced evolution via DNA integration, leading to extremely heightened abilities, or rejection via the virus, leading to the parasitic nature taking over and forming a mass of black, leech-like pustules, which can grow in size if exposed to more organic matters. The only individual known to survive the process was Albert Wesker, which was more than likely due to the fact of his previous exposure to the T-virus. Other beings that took positive mutations from the Uroboros virus include the Reapers; cockroaches exposed accidentally to the virus, who then in turn grew largely in size, gained armour-like carapaces and scythe-like appendages, explaining the name.