Make sure you set Office 2011 to automatically check for updates. This will ensure that you don't transmit a virus that won't affect the Mac, to a PC. Also, if you're only using Word, you should give Pages a try for a few weeks. You can "export" (save) your documents to Word, and there are very few compatibility issues when you open it in Word on a PC. I found Word to be a bit buggy from time to time, so I just went back to Pages.
Also, because your Mac should be set to receive daily virus updates from Apple (it updates in the background through a setting that says "automatically update safe downloads list" in the security settings), don't believe any communications (email or pop-ups) that say a virus has been detected. It's the only way, right now, to infect a Mac with a virus. That is, the user needs to agree to something to cause a virus to install. Also, if you install any Adobe programs, you'll need to make sure they're updated yourself. You might want to change the security setting that says "automatically allow signed software to receive incoming connections," because of the recent issue with certificate fraud. This way, you can decide. Or, you can set it to block all incoming connections. In Safari preferences, make sure to uncheck "Open 'safe' files after downloading." This way, if something suspicious is downloaded by accident, it will not open unless you decide to do so.
Finally, while Apple products are designed in California, they are manufactured overseas (I think mostly in China and Taiwan.)