Questions such as these are more efficiently answered in the ClamXav Forum
Scottish Phil wrote:
I recently detected a trojan virus and quarantine/deleted it using ClamXav. It came via email from a wordpress website those updates hadn't been processed correctly.
It's usually not a good idea to allow ClamXav, the Finder or any other A-V software to move or delete e-mail related files, but if it was just the attachment you probably didn't do any harm.
There is no such thing as a Trojan virus, it's either one or the other. Viruses spread by themselves and there are currently none known to be in circulation that can impact OS X. Trojans must be opened to do anything at all. Without knowing the infection name, I can't say for certain, but since over 99.9% of Trojans are Windows only, its very likely there was no danger from it, plus OS X protects you from all currently known malware as long as you keep it fully up-to-date and don't disable such protection (XProtect and GateKeeper).
I noticed a guest account popping up at login/screen refresh and I have never set a guest account.
AFAIK, everybody gets one Guest account by default, at least I always have gotten one without ever being asked. I can only guess that you never noticed it before.