This is truly an MPSIMS.
There has been a study done on long term HIV survivors (i.e. folks who never came down with full-blown AIDS) that there seems to be a correlation between their survival rate and the rate of infection with another virus GVB-C (aka Hep G). This virus appears to be non-virulent, and it’s mode of repression of HIV still has to be further investigated, but this may be an extremely important breakthrough in the treatment and prevention of AIDS.
The first thing I thought about was Jenner and the smallpox/cow-pox relationship( http://www.sc.edu/library/spcoll/nathist/jenner.html ).
I just thought I’d share.
Read more about it here: http://content.nejm.org/this_week/345/10/index.shtml