Trends in prevalence and case finding in the ALERT leprosy control programme, 1979-1999.

From 1979 to 1999, the ALERT leprosy control programme has covered a well-defined area in central Ethiopia using standardized case finding strategies. During this period, the leprosy prevalence has decreased more than 30-fold, there has been a 3-fold decrease in case detection and a 6-fold decrease in the case detection rate. The proportion of MB patients among new cases increased by around 80% and the proportion of children among new cases decreased by around 60%. Several factors may have contributed to these trends. The impact of the introduction of MDT and the shortening of the duration of the MB regimen are shown, but other factors are also discussed at length: an increase in the population of the area, cleaning up of the registers, changing case definitions, changes in staff motivation and fluctuations, even small ones, in case finding intensity and coverage. Do the observed trends reflect a reduction in the transmission of the leprosy infection? Because of the many confounding factors, it would be difficult to answer that question positively at present. Additional rigorous data collection and analysis is required.