Use of local variations in trachoma endemicity in depicting interplay between socio-economic conditions and disease.

A trachoma prevalence survey was conducted in 1960-61 in Taiwan prior to the introduction of a large-scale treatment campaign. Marked local differences in endemicity of trachoma were encountered in neighbouring administrative areas (lin). Use is made of these local variations in depicting the interactions between socio-economical factors and endemicity of the disease.The study demonstrates the interaction between the socio-economic development of the household, on the one hand, and of the community of which the household forms a part, on the other. In a community of low trachoma endemicity, persons who do not share in the general socio-economic level of development nevertheless benefit from a low risk of infection, while in a community of high endemicity those in the upper socio-economic groups suffer from an enhanced risk of infection, though to an appreciably lesser extent than the general average for the community.The study indicates a possibility of an absence of association between various bio-physical environmental factors; for example, in a small community, better housing does not necessarily mean a better water supply. However, if any of the factors are considered, whether there is an implied pattern in the other factors or not, the most striking index of relative prevalence appears to be provided by the number of persons per unit (i.e., ping; about 3.3 m(2)) of sleeping area.