IRC is like you say E-mail, or World Wide Web. There are hundreds of IRC programs out there.
To my knowledge, we have a link to mIRC on our site. While I doubt they have a trojan there, if you think this may be the case, you should probably contact the site where you found the trojan.
Myself, I don't really trust antiviruses. I really think many give fake warnings, just to give you the impression they are doing something useful.