Anti-Virus is a very fast paced industry. It used to be a few years ago (when I was knee high to a grasshopper) that viruses were written for fun or to show off a programmers skill. However now it is a multi-billion dollar industry involving data mining, fraud and other nefarious activities.
Most anti-virus companies release constant patches as they are able to isolate viruses and neutralise them. Most good anti-virus programmes will also try to quarantine the rogue code and somehow safegaurd your system, but all of this can only go so far.
You'll find some step by step guides to removing the virus through a Google search, but prevention is always better than cure.