“Most probably it wasn't mIRC at all that got you infected.”
mIRC doesn’t get people infected, it’s people lack of common sense which gets themselves infected. Yea maybe the Transferred files over IRC was the source of how you received the Infected Files but its Lack of common sense which gets anyone infected. People should know by now not to execute files unless sent by very “trusted” sources (who had your authorization to send, with informatics about the files) and even then you should scan the files before executing them with an properly Configured/Updated AV, AT Cleaners. Because even “Trusted” sources may have spread which they aren’t aware of themselves do to no AV & AT or lack of laziness to properly Configure/Update the AV, AT Cleaners and run Manual Scans on these files downloaded.