Hi,
OK I know I am about to spell this wrong but here goes.
RI stands for respiratory infection - sometimes you will also see URI - upper respiratory infection.
Signs include bubbly mucus in the mouth and the back of the throat, sounds when breathing (clicks pops and wheezes ), open mouthed breathing and sitting with the head elevated to try and help with the breathing.
You can also sometimes see traces of the mucus in the waterbowl or smeared on the cage furnishings.
dr del