R.I is pneumonia. Your snake can get it from a ton of different things. The most common to cause it are prolonged stress(snake not getting the proper accumulation period,ie being handled to much when the snake first arrives,no hide box,being house with other snakes,etc.) or what seems to be the most common is to low of temps on the hot side. Some seem to get over it with just a raise in there hot side temps if all other conditions are right and some need 30 days of treatment on the proper meds. I.E getting a culture done to insure you start off with the right meds. instead of having to switch down the line. There are a ton of other ways for a snake to get R.I though so dont think the ones i listed were the only ways. They just seem to be the most common ive seen with ball python owners.