Virusfree cultivars can be made 'variegated' by infection with the virus. In camellias, this was not yet really successful, and thus there is doubt wether or not there is a single strain, or several, of virus, or viruslike agents. Single cultivars may or may not show signs of infection. Some cultivars show leaf mottling only if they are not in their best physiological condition. Once infected, it is not possible to cure the plant.
Seedlings are, usually, free of virus.
Virus infection is mostly man-made. The infection is easily carried to healthy specimen by cutting flowers or scions, where knives and scissors are not cleaned between different bushes. Whether other vectors like aphids are important is unknown. The cleaning procedure of cutting tools is not established. Somebody claimed that a clean virus is thus transferred.