What happened to sanatoriums?

The movement spread to every continent throughout the world. It ended when chemotherapy was developed that cured the disease. Admission to sanatoria declined, and the sanatoriums began to close. By the middle of the twentieth century most had been closed and had been converted to other uses or even demolished.

Is there a difference between a sanitarium and a sanatorium?

The terms sanatorium and sanitarium are interchangeable, however, sanitarium is primarily a North American word. The difference between the words is their origin, though it is not much of a difference. The word sanitorium is derived from the Late Latin word sanitorius, which means health-giving.