Kharaa Bacterium
The Virus is an affliction that seems to be all over Planet 4546B. It is described in the Degasi PDAs as "part of the ecosystem". It is suggested that the Degasi survivors were infected at some point.
Afflicted creatures will be identifiable by the small, glowing cysts on their body.[1]
Warpers will attack infected creatures once their infection passes a certain level.[2]
The player will become infected with the Virus at a certain point in the story.[1]