Well I am not a doctor, but my daughter had shingles and this is what my gp told me - you get chickenpox, usually as a child, then the virus sticks around in your body fending off further chickenpox viruses, so it is extremely rare to get chickenpox twice. However, in some people, often due to general ill health, or sometimes as a result of stress, the virus reactivates itself as shingles. You cannot therefore catch shingles, you would actually catch chickenpox from an infectious person (if you hadn't already had it), and this can be very nasty in an adult or elderly person. As I say, this is what I was told by my GP, please do not rely on it if you are worried about somebody's health!