Termites and Timber rot are the biggest destroyers of homes, attacking the timber frame that holds the roof in position.
The first thing that always deteriorates or is eaten, is the bottom plate, this timber holds the wall from moving SIDE TO SIDE and holds the trusses up, there is a lot of downwards weight, so depending on the integrity of the frame, it could cause a lot of movement thus causing the waterproofing membrane to be compromised.
A lot of the time we need to remove walls on both sides to get to the damage, BUT when finished it will be as strong, if not stronger than the original as we also screw and glue the new timber to old studs.
I recommend always to fix a leaking shower as early as possible; it will cost you a fraction then if we need to replace structured walls.
A small leak can turn into thousands of dollars if not seen to ASAP, once your timber in the wall starts rotting, they lose their strength in holding your roof up, your plaster board would deteriorate and become soft, the constant moisture would promote fungus and mould and finally would become the perfect scenario for Termite infestation. You would start seeing the skirtings and carpets rotting and this would become a health hazard.
Recommendations; always do a visual for mould, dampness, and if uncertain get advice from professionals.