[Name] Las Plagas [Source] Resident Evil 4 [Symptoms] 
A parasitic, organism which can infect a variety of hosts, including humans. It has the ability to control its host's behavior, inducing a hive-like mentality among the infected and extreme hostility towards uninfected individuals. The infected retain most of the characteristics of humans such as fine motor skills as seen through their use of simple weapons such as scythes and axes, and more complicated weapons such as chainsaws and chainguns. They are seen to obey "Queen" parasites, much like ants.