Zbot Virus

I received an email from Cox a couple of weeks ago about a virus that may have compromised my network. I tried to locate it by searching for it in safe mode, I tried deleting the extension (but it wasn't installed), used McAfee and Avast to scan for malware and viruses (there were none).  I also looked for suspicious programs in the control panel of my laptop. I was told by a tech-savvy friend that if my computer isn't behaving strangely then I shouldn't worry, but the email is stressing me out. I'm not even sure if there is a virus based on the steps I've already taken.  I should also add that my computer is as fast as it ever was, with no lagging, or other issues. 

Is it possible to have a dormant virus on my computer? Is there anything else I should do?