When you say they were lost due to virus infection- were they merely deleted? Or were they infected and thus corrupted?
In the first case, file deletion software should help- though I'd advise caution as you might be restoring something that is infected and could just cause yourself to be reinfected.
http://www.cultofmac.com/67472/how-to-undelete-files-in-mac-os-x-macrx/
http://www.wikihow.com/Recover-Accidentally-Deleted-Files-in-OS-X
http://data-recovery-software-review.toptenreviews.com/mac-recovery-software/
In the second case, unless you have a backup somewhere, there's not really a way to recover that I'm aware of.
Topic: How to recover deleted files from Mac OS X? (Read 4,369 times)
