Date of Award

Spring 2022

Document Type

Dissertation

Degree Name

Doctor of Philosophy (PhD)

Department

Public Health

First Advisor

Galvani, Alison

Abstract

In this dissertation, I explore the disproportionate burden of infectious disease outbreaks, epidemics, and pandemics and the projected impact of interventions for mitigating their harm on populations in Cameroon and the United States. The spatial heterogeneity in vaccination coverage and access to care in Cameroon creates areas that are highly susceptible to measles transmission. In the US, the HIV epidemic is increasingly concentrated in the southern states in addition to larger cities with variable levels of prevention and linkage to sustained treatment. Disparities in COVID-19 burden exist by race and geography across Michigan, in part due to systemic racism and underlying health burdens.In Chapter One, I model the spatiotemporal dynamics of a large outbreak of measles in Cameroon by using several multivariate time-series models at the health district, department, and region levels. By assessing the spatiotemporal dynamics at different geographical scales, it was possible to determine the respective contribution of each administrative division to measles transmission throughout the country. The model including long-distance population mobility optimally reflected the spatial spread of measles. Population movement between departments within regions was estimated to contribute to 9.1% of all cases and movement between regions contributed to 18.1% of cases at the health district level. These findings demonstrate the need to improve our understanding of the roles of population mobility and local heterogeneity of vaccination coverage in the spread and control of measles in Cameroon. In Chapter Two, I develop a mathematical model of HIV transmission and progression to evaluate the impact of expanding HIV prevention, diagnosis, treatment, and viral suppression levels in 57 priority counties and states in the United States, as identified by the federal government initiative “Ending the HIV Epidemic”. This plan aims to increase access to diagnosis, linkage to treatment, maintenance of treatment and pre-exposure prophylaxis uptake in high-incidence counties as well as states with high burdens of disease in rural areas between 2020 and 2030. I project that the number of annual new infections could be reduced by 58% and that over 157,000 cumulative new infectious could be averted over the next decade nationwide upon successful implementation of this initiative. Despite the substantial benefit incurred by this HIV care continuum expansion, additional concerted efforts beyond its scope such as community-specific interventions benefiting disproportionately affected populations, stigma erasure, HIV criminalization elimination, and ending systemic oppression will be needed to truly stop HIV transmission in the US. In Chapter Three, I examined racial disparities in COVID-19 mortality in Michigan, US, stratified by age, sex, and comorbidity prevalence. Using individual-level linked death certificate and surveillance data on all COVID-19 deaths statewide, I calculated that the mortality rate for Black populations overall was 3.6 times that of White populations, with heterogeneity across neighbourhoods. Strikingly, the mortality rate for Black individuals under 65 years lacking comorbidities was 12.6 times that of their White counterparts. Prevalence of comorbidities, age, and sex did not account for the elevated mortality rate experienced by Black individuals in Michigan. Even after accounting for demographic and underlying health characteristics, my work highlights that disparities across race resulting from systemic racism are compounded in crises. This dissertation contributes to our understanding of the inequitable impacts of epidemics on under-resourced or historically marginalized communities within the United States and Cameroon, with analyses focused on racial and geographic disparities. Addressing the root causes of these disparities through elimination of systemic racism, improved access to care, and healthcare reform is necessary to prevent further infections and deaths. Furthermore, these changes have the capacity to reduce the impact of future infectious disease epidemics on the populations that are consistently and disproportionately affected.

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