My Mac has become a host for infected Windows office documents. I have hundreds of Office documents with other people's Windows viruses on them. Help! I regularly receive and send Word and Powerpoint files to colleagues. I have a Mac, but occasionally log into dropbox from a PC or plug my USB stick into a PC.

Recently, I started getting alerts when using my USB on a PC about possible viruses. I scanned my drives using ClamXav today and sure enough, something called CVE-2012-0013 has been found in hundreds of Word and Powerpoint files.

I am finding it really hard to work out where the virus came from, and how serious it is, but in the meantime, I need to clean up these files because I need to send them out to other Windows users.

So far I have tried several free and trialware options:
ClamXav - this is the only program that is detecting the problem, but this software can't clean files
Sophos Anti-Virus, VirusBarrier, Avast can't even detect the problem.
I also tried a PC. Spybot Norton 360 and AVG can't detect the problem.

Please, no suggestions to just delete the files or stop sharing with Windows users - there's no way around it for work! Ideas on how to prevent this happening again in the future would be appreciated - I often work with people who don't have antivirus or have outdated versions of Windows that could be vulnerable to viruses.