A Macintosh will become infected as soon as an infected application is run. Mac/INIT-29 is extremely virulent and infects applications even when they are not running. If your system is infected and you insert a locked disk, a dialog containing the following message "disk 'diskname' needs minor repairs. Do you want to repair it?". Multiple infections of applications are likely. Documents, extensions and control panels can all be infected by this virus.
This virus was first reported in June 1988.