I remember a movie, maybe made for TV, maybe theatrical (though I saw it on TV), in the 70s.
It was, to the best of my recollection, about a typhoid outbreak in some European ski area. The men investigating it suspected a connection between the toilets at the top of the mountain, and the water supply below. To prove it, they dumped red dye into the toilet, and waited for it to appear in the drinking water. Which it did.
I don’t think it was a TV episode. it seemed as a stand alone movie.
Anyone have any idea what I saw?