(Capcom's primary storyline)
Arias developed the virus as part of his plan to bring about human extinction to atone for its sins. It exists as three strains. The typical strain is waterborne and transfers from host to host via fluidic contact such as through bites. This virus is naturally dormant, allowing it by design to infect a wide area before detection. The second strain is described as the "trigger", and causes the main strain to activate and zombify its host when the two are in contact. This strain is airborne, and was intended to be stored in gas canisters to be sprayed over an area. The third strain is a vaccine which can reverse the effects of the trigger and un-zombify people. An added bonus to this third strain is that zombies infected with A-Virus will not attack those vaccinated with this strain, unlike those with the Alexander University vaccine.