Mark Allan - Software - clamXav
Installing this sofware also installs the antivirus engine, which then downloads the antivirus definitions. So you don't need to also download the clamAV package.
This software just scans, it's not continually monitoring file I/O. Also it's not automatically triggered by receiving email.
Although ClamXav is free, the author is seeking voluntary donations. (Almost never works.) I'm testing now and it it works I'll donate $20. It's nice to have a convenient scanner.
I was able to install as a non-admin user. It does create its own directory: usr/local/clamXav.