Should I install an antivirus if I have the office suite?

I keep reading different comments about whether to install an antivirus on my macbook or not. I have installed microsoft office and I wonder if my mac could get infected as a result. I've just received a warning from windows and I don't know what to do. I know nearly nothing about computers , what the right or wrong thing to do is so I would really appreciate some advice.
Thanks.

If you're running Windows, it's a good idea to run AntiVirus software.
If you're not running Windows, then you don't have much to worry about.

The antivirus is so you will not pass a MS windows virus on to other windows users should you exchange files with other windows users.