Properly named antivirus have little sense in Linux, something runs as user and have the ability to modify system executables and spread to other systems probably are only experimental at best.

But that don't take out following the by default security practices in distributions (install only from the distribution, be root only for the essentials, don't have by default enabled remote services, firewalls with everything denied by default, updating, etc).

Trojans, vulnerabilities in enabled services, or even in browsers/plugins/etc are still a concern, but those kinds of attack are not the ones that antivirus usually spot. Checking for rootkits (i.e. with rkhunter), browsers with improved security, and portknocking to make visible private services only to the people/computers that will use them are examples of measure that you can take.

And, of course, you can always install clamav in your linux mail/file server if your users use windows.