Seemingly contagious boils spread between pet rats

Question
This summer I ordered a hairless pet rat from a local pet store.  When I got it, he was not very healthy and was weak.  I tried to take care of him anyway.  

Soon he developed these boils under his skin which would form, grow large, pop open and reform.  Greenish-whiteish ooze would come from them which smelled very offensive.  He lived with my other pet rat whom I'd gotten from the same place.  Soon after he developed the boils I put Iscars in the cage with my other rat Happy Trail because I did not want him to get sick.

The hairless rat died sadly.  Around a few weeks after it had died, Iscars started getting the boils around his neck as well.  He showed no signs of illness however.  Then two weeks ago Happy Trail got a very large golf ball sized boil under her arm pit which I thought was a mammary tumor, but did burst and turn out to be the same thing.

Iscars and the hairless came from the same store, but Happy Trail didn't.  What sort of disease is passing between them and should I be worried about contracting it myself?

Bubonic plague keeps popping in my head, lol.

Answer
Those sound like abscesses or cysts to me, really. Usually neither are not contagious but their cause, given if it's bacterial or viral (usually a wound/damage inflicted that becomes infected by bacteria), can be I suppose - just as any virus can be. Cysts are VERY common in hairless and I'd be willing to bet that was the cause. I personally have never had any experience with cagemates getting cysts/boils/abscesses without a notable cause.

Did you do anything at all to treat your hairless? Bathe him frequently, take him to a vet, start him on antibiotics? Have your current rats seen a vet, how often do you bathe them, and are they living in a relatively clean environment?