The easy answer: probably not. In the 13 years I was with Apple Computer, I saw about two distinct and separate viruses on a Mac. One of them was a simple Microsoft Word virus that only affected Word documents. The other was a real-deal virus, however, Apple caught that one before anyone really had contracted it.
So, do you need Macintosh antivirus software? Probably not.
I’d be more worried about you losing your data to a hard drive or directory damage issue than getting a virus. Most people on any computer platform equate any problem–big or small–to a virus. Most of the customers I dealt with while working with Apple began with “My computer isn’t working. It’s probably a virus.” Obviously from our end, this was never, ever a virus and almost always a directory damage issue or software problem.
If you were to invest in a virus software for your Mac for peace of mind sake, I would recommend something simple as the Norton suite of antivirus software, if you really want to still run one on your system. Be aware that these types of software will possibly reduce the speed of your Mac, since it has to scan every file every few minutes.
If you are gun-shy about Mac antivirus, or, if you just have questions, just contact us at Capital Mac Service and we can cover your options!