Although it isn't really canon, Illya's hatred of hospitals is very much a part of fanon. This story is an attempt to explain this hatred. Before anyone says it, I know it could be expanded :-) In fact, it kind of ties in a little with a story I wrote some time ago called 'Unknown Fear'. One day, I may bring the two together and form a much longer piece.
Anyway, click on Glenna's artwork to go to AO3.