A hospital movement, quite distinct from that of Innocent III., which attracted so much attention shortly after the general hospital became common as to deserve particular consideration, was the erection of the leproseries or special institutions for the care of lepers. Leprosy had become quite common in Europe during the Middle Ages, and the continued contact of the West with the East during the crusades had brought about a notable increase of the disease. It is not definitely known how much of what was called leprosy at that time, really belonged to the specific disease now known as lepra. There is no doubt that many affections, which have since come to be considered as quite harmless and non-contagious, were included under the designation leprosy by the populace and even physicians incapable as yet of making a proper differential diagnosis. Probably severe cases of eczema and other chronic skin diseases, especially when complicated by the results of wrongly directed treatment or of lack of cleansing, were not infrequently pronounced to be true leprosy.
There is no doubt at all, however, of the occurrence of real leprosy in many of the towns of the West from the twelfth to the fifteenth centuries, and the erection of these hospitals proved the best possible prophylactic against the further spread of the disease. Leprosy is contagious, but only mildly so. Years of intimate association with a leper may, and usually do, bring about the communication of the disease to those around them, especially if they do not exercise rather carefully, certain precise precautions as to cleanliness after personal contact or after the handling of things which have previously been in the leper’s possession. As the result of the existence of these houses of segregation, leprosy disappeared during the course of the next three centuries, and thus a great hygienic triumph was obtained by sanitary regulation.
This successful sanitary and hygienic work, which brought about practically the complete obliteration of leprosy in the Middle Ages, furnished the first example of the possibility of eradicating a disease that has once become a serious scourge to mankind. That this should have been accomplished by a movement that had its greatest source in the thirteenth century is all the more surprising, since we are usually accustomed to think of the people of the times as sadly lacking in any interest in sanitary matters. The role of the Popes in the matter is another striking feature well worthy of note. The significance of the success of this segregation method was lost upon men down almost to our own time. This was unfortunately because it was considered that most of the epidemic diseases were conveyed by the air. They were thought infectious and due to a climatic condition rather than contagious, that is, conveyed by actual contact with the person having the disease or something that had touched him, which is the view now held. With the beginning of the crusade against tuberculosis in the later nineteenth century, however, the most encouraging factor for those engaged in it was the history of the success of segregation methods and careful prevention of the spread of the disease, which had been pursued against leprosy. In a word, the lessons in sanitation and prophylaxis of the thirteenth century are only now bearing fruit because the intervening centuries did not have sufficient knowledge to realize their import and take advantage of them.
James J. Walsh, The Popes and Science (1908)