If you want to have fewer problems with linux its a good bet that the less you install and change, the more compatible it will remain.
I put an anti-virus on my mac (virus barrier x4) which will scan other computers on the network, except linux because its so hard to get linux to cooperate in that department. In the last 3 years I have had zero viruses on the mac but it did come in handy for scanning my win98 and removing viruses because you can no longer get up to date anti-virus programs for win98se.
Although linux is based on a more complicated and awkward OS, it still has the same basic Unix under-pinnings as the Mac does so it will be difficult to run into virus problems unless you do silly things like click on links in email. Even then, you'd probably just proliferate windows viruses and send them onto someone else rather than causing yourself issues. Besides, why bog down the OS to scan for Viruses? The only virus program I know of that doesn't hog all cpu resources in virus barrier because it only checks for viruses when files are created or changed, or when you tell it to scan everything.
Be assured. Viruses are not much of an issue with Unix based systems. Don't worry about it. You're not running windows... right?