A mathematical construct of epidemiological time trend in tuberculosis: a fifty year study

Balasangameshwara, V.H.; Chakraborty, A.K. and Chaudhuri, K. (1992) A mathematical construct of epidemiological time trend in tuberculosis: a fifty year study. Indian Journal of Tuberculosis, 39. pp. 87-98.

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Abstract

A 50 year mathematical iteration of the tuberculosis situation has been prepared using the available demographic, epidemiologic & technical information and applying some assumed values for efficiency of intervention measures (i.e., the district tuberculosis Programme-DTP). With out an organised intervention and with a population growth rate changing from the initial value of 2.2% per year to 1.9% in 50 years, the prevalence rate of infectious cases is likely to fall from 0.39% to 0.26%. However, with the application of alternative higher figures of reduction of growth rate, distributed in a hypothetically staggered manner over a 50 year period, to reduce it from 2.2% to 0.8%, the case rate would register a slower reduction- from 0.39% to 0.29%. On the other hand, the application of case-finding with 40% efficiency and all cases treated with Standard Regimen (SR), the prevalence rate of cases in 50 years is likely to register a fall from 0.39% to 0.18%. The proportion of smear positive cases among them is likely to fall from 43.73% to 27.89%, under the above situation. After a period of 30 years of organised intervention at uniform casefinding efficiency of 33% and all cases treated with SR throughout the period, the prevalence of infectious cases would be 0.22%. However, assuming that the efficiency of case-finding and treatment cannot he taken as uniform throughout the period, various mixtures of efficiency of interventions in the form of casefinding and treatment inputs have been considered, varying these with time. Validation of the projected infection rates available from the mathematical model has been done by matching the observed infection rates with the projected one in the model and relating it to the programme efficiency.

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