Use of local variations in trachoma endemicity in Taiwan to elucidate some of the clinical and epidemiological aspects of the disease.

A trachoma prevalence survey was conducted in 1960-61 in Taiwan prior to the introduction of large-scale treatment operations and marked local differences in trachoma endemicity were encountered among adjoining neighbourhoods. Use is made of these local variations in depicting differences in the salient clinical and epidemiological features of trachoma under various degrees of endemicity.The study suggests that a reduction in the risk of infection is first reflected in a lowering of the intensity of clinical signs and in an increase in the spontaneous cure rate and is followed later by a reduction in the incidence and hence, in the long run, in the prevalence of the disease.A scoring system applied to all cases (active and healed) reflects spontaneous cure and gives a more accurate index of endemicity than either of its 2 components relating to intensity or gravity.