G'day colinhawkes103,
In answer to your question, I have reinstalled (see reasons below) ClamXav 2.6.4 from THEIR download page <http://www.clamxav.com/download.php> ONLY. It works fine and is up to date with current Mac virus definitions. It works unobtrusively and does not slow performance. DO NOT download ClamXav from Apple's App Store as several pivotal elements are NOT included (e.g. ClamXav Sentry).
Additionally, I installed open source (ALWAYS free) anti virus software Avira and OnyX. They operate differently and certainly reassure me that all is well (?) with my Mac. Being quite quick but effective in scanning, I use Avira daily as I no longer have boundless confidence in Apple's OS X after months of catastrophic data loss, HD erasures/OS X reinstallations, non Apple apps reinstallations/reregistrations, ad infinitum, ad nauseum!
Mavericks has traumatised me since installing 10.9.2 update. 10.9.3 was even worse. in 10.9.4, problems are resurfacing. Preceding banter over "Mac virus / NO Mac virus / malware" are non constructive semantics and do a great disservice to genuinely concerned members. I hope this helps.
Sincerely, Paul Ranger 1.