I have walked the Camino twice, starting both times from Le Puy.
I am not Christian and so my reasons to walk it were not religious but personal.
It was my first try of a "long distance trail" which got me hooked on these kind of trails, like the AT, TMB and more.
I can describe this experience best by transferring the feeling of a long distnace hiker first. After walking for 5 to 7 days your body adjusts to the hardness of the trail leaving your mind to soar up,
you find yourslef walking like an automatic pilot, you walk and your body sense the trail while your mind is doing nothing else but high level meditation.
It's an experience no one can avoid- you walk almost all day long, the noises and sounds you hear are the wind, rain, leaves, trees, birds, your breaths, the squeaking of your pack- all these are the ideal recipe for a high level meditation and this is the feeling you get addicted to, this is what made me and others come back and walk more long distance trails.
Now, add to this the experience of the many people you meet, the encounters of people and countries not familiar before, the sharing, caring, attention from other people is intoxicating, you feel like you are trully not alone, you can trust almost everyone to do everything to and for you, where else, in these stormy time, can you find this eperience? many like me wish to feel it again and again and this why many go back.
It is a feeling of physical and mental strength that rises from within you and make you feel like you can conquer the world, nothing is hard from that point on.
Infectious?oh yes, I have become a missionar for the Camino and long distane hikining in general, I try and succeed convincing my friends and strangers I meet on the net to walk th Camino.
Every spring my feet itch and I plan to walk another trail that year if I can , I constantly plan on which trail I should walk and there are so many of them but the camino is a life changer for me.