Wow, I never realized that is where that rhyme originated. I don't think I'll ever look at nursery rhymes quite the same again.
I'm betting that the senators from that state have something to do with these cases of plague.
Virtually all nursery rhymes are either allegories or 'training songs' as it were.
Its not particularly well presented, but for a good outline of some, take a look at
http://www.wowessays.com/dbase/ad1/aym107.shtml
Note, the website's analysis of ring-a-ring-a-rosey uses the British / Australian variant, which goes atishoo atishoo we all fall down, and also has a claim that it could in fact be a hindu chant in any case. take a look.
Sadim