Viruses come in many forms in fiction. When they don't just kill people, usually viruses turn people into "infected" slaves or into entities subservient to the virus. The transformation is both mental and physical. The converted will have unflagging loyalty and be instantly ready to commence villainous actions. If the converted still resemble their previous selves, they will use their personal knowledge to prevent their former loved ones from doing them harm, or from trying to get them back.
Despite the body snatching, if a virus is only able to crudely mimic human behavior it may lead to a Glamour Failure that's especially noticeable. If the virus mutates their host to the point where they are almost unrecognizable, expect it to do the same to environments. How much of the former person is left after infection depends on the series, as does whether or not the process is reversible. It also depends on whether it's a main character or not, they can sometimes use The Virus' powers against it with enough willpower and even spy as a mole for a while. If one of the villains use their willpower, then they tend to end up on the high end of the Elite Zombie chain.
If the virus is sentient, then more often than not it is also a Hive Mind with a Hive Queen directing it.
Viral Infections can be considered very nasty and devastating in the Outskirts Battledome. Some activate instantly, others take a bit more time. Many times viruses in fiction will cause a person to become one of the Undead. Many of these viruses in fiction are transferred through direct contact, however others simply need fluids or even can become airborne.
Universes that include Viruses are:
- Most Zombie, Vampire, and Werewolf series
- Buffy the Vampire Slayer has the vampires it is famous for.
- DC Comics
- Digimon typically deals with computer viruses, with many digimon actually being classified as virus types.
- Doctor Who
- Final Fantasy, specifically 7 (more specifically that garbage Advent Children) had Geostigma
- Marvel Comics has several. The zombie virus that led to the kinda meh Marvel Zombies idea and your standard vampire virus, the legacy virus, the technorganic virus, etc.
- Real Life has shit-tons, most notably the Black Death that killed an estimated 100 million people in the 1300s
- Resident Evil has the zombies that are central to the series.
- Starcraft has the Zerg which are typically like this though they aren't actually viral life-forms.
- Star Trek
- Warhammer 40,000
- Poison Manipulation