Help! explain how a childhood disease can reoccur in a different form in the sensory nerves of the thorax..

It is also possible for similar bacteria to cause different symptoms and a different symptomology in someone. I have personal experience with one of these. Streptococcus bacteria are fairly common, and some of us have had strep throat more than once, including me. It is painful and causes a fever, but it is usually fairly easily defeated by an antibiotic.
However, these same strep bacteria can get into the general circulation and invade the entire body, not just the throat. A red rash and a very red tongue and inner mouth is a giveaway for this, and often there is no sore throat. This is a very, very dangerous disease which is systemic and causes a very high fever and has the potential to damage heart valves, kidneys and other organs if it is not stopped. It can also be lethal, although these days not so much. The disease is scarlet fever, which I contracted when I was 7 years old. This was in the 1950's and I am allergic to penicillin so they had to give me a less effective antibiotic. I was hospitalized with a fever of over 105 degrees, and thank heavens I was so young because small children can handle higher temperatures than adults can. I was lucky. I survived and have no heart or kidney damage, but it was very serious back then.
I don't know if this answered your question because I'm not sure which disease you're talking about, but some basic childhood diseases can take a different form in adults. Measles, for example, can lead to shingles in adults because the immune response is different in adults than it is in children.
Our immune systems do not become fully functional until we are about ten years old, which is why childhood diseases are diseases of childhood; we do not yet have full immunity against them. Today, there are vaccines that still were not available against certain diseases when my son, who is about to turn 28, was a child. He contracted chicken pox at the age of 4, and people of my generation almost always also had chicken pox as kids. I could care for him because I had chicken pox when I was a child and I am immune to this disease because of it, as is my son now. However, a few years later he could have had a vaccine to prevent him from having the disease at all.
Immunology is a fascinating field because different antibodies react differently to specific antigens.
I hope this helped. I'm not sure exactly which disease you meant, so I had to give a very general answer.