Tuberculosis Drug resistance Model

The high prevalence of tuberculosis in developing countries and the recent resurgence of tuberculosis in many developed countries suggests that current control strategies are suboptimal. The increase in drug-resistant cases exacerbates the control problems. Currently employed epidemic control strategies are not devised on the basis of a theoretical understanding of the transmission dynamics of Mycobacterium tuberculosis. We have developed a theoretical framework based upon mathematical transmission models that can be used for understanding, predicting, and controlling tuberculosis epidemics. This theoretical framework can be used to predict the temporal dynamics of the emergence of drug resistance, to predict the epidemiological consequences of epidemic control strategies in developing and developed countries, and to design epidemic control strategies.

We have coded up a program to predict the annual incidence of disease (due to drug-sensitive and drug-resistant TB) per 100,000 using the model developed in the following papers:


Applet 1. Annual incidence of disease per 100,000 for drug-sensitive and drug-resistant TB.

Instructions

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This applet graphs the annual incidence of disease per 100,000 people each year. The green line represents the incidence of drug-sensitive strains each year while the red line represents the incidence of drug-resistant forms of tuberculosis.

To change a parameter in the model just select the parameter you want to change by using the drop box. Enter the new value for the parameter in the text box and click the 'Set' button. Click on the 'Graph' button and the simulation will run. Each time you hit the 'Graph' button the simulation advances time by another 100 years. Note that the effective reproductive rates (RS and RR) have been calculated for you. Click here for a brief explanation of fitness and the role of the basic reproductive rate.

We have setup the model so you can change the following parameters:

  1. delta, the efficacy of treatment of a drug-resistant case relative to a drug-sensitive case (delta can range from 0.0 to 1.0). If delta is set at 0.0, this implies that the treatment regimen is completely ineffective in curing a drug-resistant case. If delta is set at 1.0, this implies that the treatment regimen is as effective in curing drug-resistant cases as in curing drug-sensitive cases.

  2. alpha, which represents the reduction or increase in infectiousness of drug-resistant strains relative to drug-sensitive strains (alpha can range from 0.0 to 1.5). If alpha is set at 0.0 this means that drug-resistant strains cannot be transmitted. If alpha is set at 1.0 this means that drug-resistant strains are as transmissible as drug-sensitive strains. If the value of alpha is set at 1.5 this means that the drug-resistant strains are 50% more transmissible than drug-sensitive strains.

  3. F, which represents the fraction of cases treated (F can range from 0.0 to 0.9).

  4. r, which represents the proportion of treated cases per year who develop acquired drug resistance (r can range from 0.0 to 1.0).