Yes, this is very interesting stuff!
In Sweden there is a study going on about the possibilities that a virus can cause back pain. A microbiologist, an infection disease doctor and a spinal surgeon (Peter Fritzell) are working together with this.
The theory is that some of the very many cases of back pain (where no apperent reason for the pain can be found), the pain acctually comes from infection. The guess is that this infection is very tiny, is causes no other discomfort for the patient other than back pain, and therefor can not be diagnosed very easily.
A first result of the study is planned to come 2006.
I don't have very much more info on this now, but this sure is interesting!
/Kris L.