:( sick rat?

No it usually will never go away. The symptoms will subside a bit but will always be there.

Breeding, Bedding changes and so forth can cause flareups caused by stress.

One more question, is this something that can be passed to others or through genetics or is it just something that 1 out of 100 could get and is no harm to rest of the group?

It can and will be passed on to the babies. So any babies produced from her should be fed off and not held back..

There is a chance not all will have it. But when breeding for food its something that happens a lot, as most wont treat breeders. If they have mycro and are breeders, i feed them off in timely manner.