This is prevalent...PN seems to pick and choose it's victims at random. I know for a fact it's not random, but we do not have all the pieces of the puzzle in front of us right now. Some day in the future it will be blatantly obvious, but our job now is to forge that path.

In my career as a public servant of 27 years(and I say that with reverence), in an urban environment, I was in contact on a frequent basis with humans living under a bridge(etc), drug user, alcohol abuser, completely subject to the environment/weather/insects/predators/etc, and when I retired over 20 years later many were still there. The ones that died usually died from another hand. My point is that what causes PN for some will never cause it for another...so we need to dig deeper......waaaaay deeper to fine the cause, and it is an elusive son of a ................