Date of Award

January 2025

Document Type

Open Access Thesis

Degree Name

Master of Public Health (MPH)

Department

School of Public Health

First Advisor

Virginia Pitzer

Second Advisor

Ying Chen

Abstract

Introduction: Typhoid fever represents a significant burden of disease in urban areas across South Asia. While the recent implementation of routine typhoid conjugate vaccinations (TCVs) has demonstrated significant protective effectiveness against disease, it fails to mitigate environmental transmission through contaminated water, which individuals without access to improved water sources (IWS) may be infected by. Objectives: The primary aim of this study is to estimate the potential reductions to typhoid fever incidence that populations could experience when increasing proportions of the population that have IWS across three high-burden cities in South Asia. The relationship between this reduction and the proportion of water-borne transmission and the overall basic reproduction rate will be additionally explored. Methods: Transmission dynamic models were fitted to data from a TCV trial in Dhaka and surveillance data from Karachi and Kathmandu to estimate transmission parameters for each site for those with and without IWS. These parameters are used to simulate the reduction in incidence with increasing proportions of IWS. Results: Incidence is reduced by less than 2 percent in both Dhaka and Karachi, and more than 93 percent in Kathmandu when increasing the proportion with IWS with and without vaccination at baseline transmission parameters. Increasing the proportion of water-borne transmission and decreasing the overall R0 yielded greater reductions to incidence compared to baseline. Conclusion: Increasing the proportion of the population with access to IWS has the greatest potential to reduce typhoid incidence in urban areas of South Asia where the overall basic reproduction rate is low, or the proportion of water-borne transmission is high, with and without vaccination.

Comments

This is an Open Access Thesis.

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