The general thought usually is that macs don’t get viruses. Myth or truth? Myth! Macs can get and send viruses, but they are just less susceptible at doing so than PCs. 
Why? Mac OS 10 has some heavy security built into it that prevents many malicious code from attacking the computer. However, the operating system does not have so much security built into it to prevent sending viruses. Also, macs are more prone to receiving viruses from another mac than a Windows computer.
So, if in a heavy mac environment, it makes sense to install the new Norton Antivirus 11 for Macintosh to protect the whole mac network. The Norton Antivirus software is an automatic process where it updates and scans for viruses periodically on its own. So, after you install it, you are in good hands. It will block viruses and let you know if there is a potentially malicious file. If you only have one mac, it is usually safe to assume you will be virus-free, but not 100%.
One thing to note is that you will probably need to call in a specialist, like New York Computer Help, to remove a virus. If you are infected, it is typically through a bad code or worm and manual removal is required. So, before you get to a precarious situation, it is better to be safe than sorry.