Mites that live on you, breed on you, and bite you, can and will reproduce outside of your body, if they must. Therefore re-infestation is not only possible, it is quite likely.
Now, that you have a working solution, you may want to keep it up just like you clean your teeth or clean your house...
That "outside of your body" can be on clothes, on the floor, on your pets, on your house plants. Because these mites are near-invisible, I don't know where they are doing this off-body activity...
But, in my experience, they are coming back, so don't stop the treatment once you feel better.
If and when it's worked out, I'll make the treatment easier... and I said if and when... Let's hope.
Now about the question: Are mite infectious?
I am sure this worries you and your friends a lot.
The answer, as unsatisfying as it sounds: yes and no.
For example this student of mine has occasional visitations by ear mites from her daughter. She must have an unattractive chemistry for those mites, nevertheless, they will stay on her, but won't breed.
Her son: no ear mites. Her husband: no ear mites.
I am like a hoover: everything loves me, finds me tasty, and a good home... Why? haven't figured it out yet.
If it were infections, chiropractors that must touch you, hug you, would be plagued, and some are, and some aren't... you see, it has more to do with your chemistry, than with you being in contact with people who have mites.