Limewire doesn't contain viruses. LW is just a file sharing program. The files come from the people that use it.
LW doesn't have a central server. The files come from each individual computer(you and me) that share files on LW. Everybody is free to share whatever they want. So you have to be careful what you download and scan each file before opening it.
Some good info in this thread:
WARNING: Viruses on network you should be aware of!
Another good thread:
Anti-virus protection and so on