Eskimo: an epidemiological simulation kinetic model for tuberculosis.

Abstract

A simple, easy to use, kinetic model allowing the simulation of the main epidemiological parameters of tuberculosis and of the financial costs associated with the implementation of different anti-tuberculous policies, has been developed and described. The model, which has been denominated "ESKIMO" (Epidemiological Simulation Kinetic Model) can be utilized on a personal computer and requires, for its use, the knowledge of a series of easily available census data relative to a given country or geographical area, an essential epidemiological profile of the disease in the same area and data which characterize one or more antituberculous treatments in therapeutic and financial terms. The rationale of the model, which is a multicompartemental system, derive from an analysis of the relationships (transfer rates) between sub-populations of individuals in relation to tuberculosis either when the dynamic state of the system is governed by "natural forces" (no treatment) or when an external action is applied to it with an aim to alter its internal pathways in a favourable sense (vaccination, long-term hospitalization, chemotherapy). The model is based on the assumption that the main objective of any antituberculous program is the reduction in size of the subpopulation of patients who can infect other individuals and therefore perpetuate the disease. Validation and projection tests carried out through Eskimo seem to indicate that concentrating the analysis on the effect of various treatments on this group of patients simplifies the calculations while the relative precision of the estimates of other parameters is very satisfactory. The results of several simulations substantiate and quantify the opinions expressed by several experts in the past that the policy of applying cheap regimens of low efficacy to a relatively small fraction of the patients' population, as frequently done in developing countries, not only does not alter the trend of the disease but produces essentially negative results (increase in the number of new cases and in the frequency of resistant M. tuberculosis). Treatment with highly effective regimens of the same number of patients as those treated now (constant coverage) and therefore without the extra costs resulting from the improvement of the available sanitary infrastructures, produces much better results in clinical terms and overall saving of financial resources.