While no system is 100% safe from viruses and malware, on my Linux machine I am guilty of not installing any AV. In the last decade or more, I have had no reason to -- although times may be changing. My web browser does not have flash, pdf readers are disabled, I'm always prompted on downloads, and Java can only run under user 'ohgodno' (and yes, it does have a passwd.)

In most cases if there is an issue with a Linux machine, you can wipe out a user and their files to remedy the problem -- the core system is very rarely impacted.