Yes, the last thing you want to do is get an established animal sick, or give it mites from the new animal. 99% of issues will show up within 90 days of acquiring an animal if it has any.
You want to prevent contact of any kind. You should house the new snake as far away from the established animals as possible. Don't handle one snake and then the other, you should at least wash your hands, but if possible only handle your established snake(s) on one day, then any new animals the next. This significantly reduces the chances of transferring anything. Finally don't use any tools or cage decor with both animals. (At least not without out thoroughly washing/sanitizing first)
These procedures in most cases are overkill, but if a new snake is carrying something nasty they are well worth the effort.