(Capcom's primary storyline)
As the A-Virus naturally becomes dormant in the human body until contacted by the "Trigger" gas, humans do not show visible side-effects for some time. This is different from people infected with various t-Virus strains, who typically mutate upon initial infection. When the A-Virus is activated, however, a similar mutation will take place as veins become varicose and discoloured, putrefaction of the skin also takes place. This may be for the same reason as t-Virus zombies, who cease providing energy to the skin as a form of conservation. They may also suffer from a loss of iris causing their eyes to turn white and in other cases become red.
Zombies lose the same brain faculties as t-Virus zombies, though people vaccinated soon after transformation do not appear to suffer from brain damage. Similarly, however, they become driven by base instincts such as the need for flesh to stay alive. They also ignore those inoculated against the virus, making the virus more attractive to terrorists who can feel safe.