I find often we are saying to "avast! for Linux/Unix users" that the Avast! on demand scanner is a safeguard against infecting a Windows partition, or a Windows Computer you may be interacting with.
It's a very different situation from running an AV in Windows.
Linux System files are mainly only affected by Virus if the User logs in as 'root', persistently, or leave it in 'Super User' (su, sudo) modes, offering a hole for port scanners to detect and maybe enter.
With common sense we should really only be finding the rare Windows virus, dependant upon the user's habbits.
