Date of Award

January 2026

Document Type

Open Access Thesis

Degree Name

Master of Public Health (MPH)

Department

School of Public Health

First Advisor

Ted Cohen

Abstract

Tuberculosis (TB) transmission is sustained in part by asymptomatic disease states that limit the effectiveness of passive case finding interventions that rely on symptom-based diagnosis. Here we develop a transmission model that represents the duration of asymptomatic disease with a gamma-distributed waiting time. By chaining multiple asymptomatic sub-states, we find that the gamma-distributed model provides a better fit to the observed distribution of the duration of asymptomatic disease than a simple one-state model which imposes an assumption of an exponentially-distributed duration of asymptomatic disease. Comparing the fitted gamma-distributed model and the simple model, we quantify how assumptions about the distribution of the duration of asymptomatic TB affect future disease trajectories and the expected impact of active case finding (ACF) interventions. Using India as a case study, we found that the more realistic gamma-distributed model projects a slower decline in TB incidence under the status quo, but a substantially larger reduction in the projected incidence of TB when ACF is employed, compared with the simple model. These results suggest that ACF interventions in high incidence settings with slowly declining epidemics like India may have larger impact and more favorable cost-effectiveness than previously estimated.

Comments

This is an Open Access Thesis.

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