Like others have said everyone is different.
But my story is somewhat similar to Traveler's. And my theory is that it is highly related to gut health, which of course in turn is related to our immune system.
I was bitten at age 7 and I clearly and vividly remember it. My mom took me to the school nurse who removed it. I remember how engorged the tick was.
But I led a fairly "normal" and healthy life. I was diagnosed at age 17 with Stage 4 endometriosis which some believe is an immune dysfunction disease. And my LLMD said 90% of his female Lyme patients have endo. But that's another story. I was able to work, finish college, travel; Live Life!
My world changed rather suddenly and drastically though in 2002/2003 at age 28. I had taken about
6 different ABX within a 6 week time frame. I don't know what they were and the docs kept giving me the wrong ones. But I know they were VERY powerful. I had shots, orals, and IV's. I now believe that I was given some from the fluoroquinolone group and I am one of the many who has suffered the consequences. One day I will look into it.
Within a month I was a different person. Bed ridden, major thyroid malfunction, severe candidiasis, food intolerances, nail ridges/pits, skin rashes. It took me about
7 years and drastic lifestyle change to overcome the candida. I had been to countless doctors and ended up self treating for the yeast. But I did and was slowly able to start working part time. But was never the same, still seeking answers from doctors. Then in 2013 I came down with mono(which of course I had to demand the test for because my doc didn't believe me.) And I have essentially been house bound since.
So my theory, at least for my case, is that I was happily and symbiotically living with the borrelia this whole time. But it wasn't until that major onslaught of hardcore ABX, that the symbiosis got tweaked and the Lyme was able to take over and has gradually dug it's tentacles into every aspect of my body and life since. I mean, as someone mentioned, we have been living with ticks for millennia. Someone posted too, (I'm sorry I don't remember who) how this class of ABX can do just that. I truly believe that is what happened to me. I am not against ABX, in fact I am seeking IV ones for my jaw infection, but I think it's quite an interesting theory.
Here's a quote from the article the above person posted:
"As mentioned in 'Lyme Toxins: the Primary Cause of Your Symptoms,' (Townsend Letter, April 2007), certain classes of antibiotics can activate bacteriophages, viruses. An astonishing new finding was released by John Travis in Science News (July 2003;164). Travis reported that research performed by John F. Prescott found that certain antibiotics, such as the fluoroquinolones, the class of antibiotics that includes the name-brands and generic brands of Levaquin™, Cipro™, Tequin™, and Avelox™, actually are known to trigger a type of virus called bacteriophages (viruses that can infect bacteria), to change the genetic sequencing of the bacteria, causing the bacterium they have infected to start producing toxins. These viruses can act as genetic delivery vans, invading bacteria, such as spirochetes, and often lying dormant until activated by a change in the host (your body) environment. Once activated, these viruses insert their toxin-generating genes into the bacterial chromosomes. These viruses can turn basically harmless bacterium into killers through this genetic sequencing of toxins (Travis 2003)."