The reason the ClamXav documentation tells you what you do with the files is up to you is that ClamXav does not attempt to repair files -- an unreliable and risky process.
In this light, trashing these files is the best course of action. Provided you have never opened them and they cannot infect your Mac -- a Windows .exe virus, for example --, you should be safe. Should you have inadvertently opened a Microsoft Office file, for example, containing a malicious macro, you might want to further investigate the matter and ensure that your installation was not compromised.
In any case, you can run a system-wide scan with an updated ClamXav as well, to be on the safe side.
Let me know if this helps!