A virus is a microscopic particle that can infect a host cell. Viruses are incapable of replicating without infecting a cell. At their most basic state, they are genetic material contained within a protective protein.
- "The Abyss" - A virus found deep underwater that allowed for deep sea animals to adapt and survive.
- "Ancient virus" - A virus long since fused with queen ants. All queens that descend from an infected queen share her traits.
- Norovirus - A genus of RNA viruses, of which Norwalk virus is considered to be the only known species.
- Poliovirus - A species of RNA viruses, which causes Poliomyelitis (otherwise known as "Polio").
- Progenitor - A virus existing naturally within the "Stairway of the Sun" flowers in West Africa. Those who are not killed from the infection become incredibly strong.
- Ebola virus - An RNA virus endemic to the Ebola valley in the Democratic Republic of the Congo.
- SARS coronavirus - A species of RNA viruses, which cause SARS. It was among the RNA viruses involved in bio-weapons research.
- Clay virus - A protocanonical equivalent to Progenitor.
- Immortality Virus - A mutagen developed by Alex Wesker, under the authority of Oswell E. Spencer.
- MS-Virus - A "Matchless Soldier" virus, made by Umbrella Lab in Raccoon City.
- Prototype Virus - A Progenitor variant used to augment the Wesker Children.
- Tyrant Virus - The term given to a series of modified Progenitor viruses.
- T-JCCC203 - A modified t-Virus used as an experimental medicine, which resulted in "Dorothy".
- Neo-t - A virus developed by Mylene Beardsley before the development of the G-virus
- t-Veronica virus - A variant of Progenitor created by augmenting its genome with that of the ancient virus.
- "t+G" - A t-Virus variant created by exposing it to G antibodies.
- t-Abyss - A t-Virus variant created by TRICELL alongside the FBC, combining "The Abyss" virus and the t-Virus.
- t-Phobos - A virus developed by Alex Wesker that triggered mutation when the subject experienced fear, unless they were able to overcome it, adapting them to the virus.
- A-Virus - a new virus strain that is capable of having its infected distinguish between friend and foe, also known as "Animality Virus," created by Glenn Arias in association with the remnants of the Los Iluminados cult.
- G-Virus - A mutation of the Type-B Progenitor variant that increases cellular reproduction - making the infected essentially immortal.
- Uroboros - Another man-made variant of Progenitor, developed in conjunction by Albert Wesker and TRICELL.
- C-Virus - An infectious agent, developed by The Family and Carla Radames, that is a cross between an advanced strain of the t-Veronica virus and G-Virus.
- Cameron Virus - An unidentified virus created by Dr. Cameron as she treated herself for infection. Those infected can move their consciousness into other organisms, allowing them to escape undetected.
- Progenitor - The Makino universe equivalent.
- Anti-virus - The only compound capable of purging the T-virus.
- "Marburg virus" - A hemorrhagic fever virus in the family Filovidae, related to the Ebola virus.
- T-virus - The Anderson universe equivalent.
- T-virus - The WildStorm universe equivalent.
- T-virus - The Perry universe equivalent.
- G-Virus - The WildStorm universe equivalent.
- G-Virus - The King's Foundation universe equivalent.
- X-virus - A virus only present in DC-canon.
- Chimera Virus - A virus only present in "to the Liberty".
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