Applied Epidemiology of Infectious Diseases in the Western Pacific: Studies from Fiji, Tonga and Australia

Abstract

This volume presents four projects and additional public health experiences, which satisfy the competencies of the Master of Philosophy in Applied Epidemiology (MAE) program. Between February 2024 and December 2025, I undertook an MAE field placement at The University of Queensland's Operational Research and Decision Support for Prevention, Control and Elimination of Infectious Diseases (ODeSI) team.

In Chapter 1, I present an analysis of COVID-19 mortality in Fiji in 2020-22, where I conducted descriptive, statistical and spatial scan analyses of COVID-19 deaths. My statistical analyses showed that older Fijians and indigenous Fijians (iTaukei) were more likely to die of COVID-19, as well as more likely to die at home. My spatial scan analysis also found evidence of significant spatiotemporal clustering of COVID-19 deaths, again with marked differences between ethnic groups in the location and size of clusters over time.

Chapter 2 presents an investigation of an outbreak of Pseudomonas aeruginosa infections at a health facility, conducted with the Gold Coast Public Health Unit in Queensland, Australia. During this investigation, I was part of a multidisciplinary outbreak control team, which conducted environmental and epidemiological investigations to identify the cause of infection and prevent further cases. I determined that the likely cause of infection was the introduction of P. aeruginosa into cases' joints during intraarticular injection of contrast, which had been contaminated due to unhygienic handling and storage practices.

In Chapter 3, I present a systematic review of global lymphatic filariasis (LF) post-validation surveillance (PVS) activities in 2025, which was conducted to inform my design of a PVS system for LF in Tonga. The review found considerable heterogeneity in the implementation of PVS. Financing and resource constraints underpinned many challenges to PVS implementation, while institutional commitment is a critical enabler of sustained surveillance.

In Chapter 4, I present my design of a PVS system for LF in Tonga. I conducted a qualitative study where I interviewed key informants in the Tonga Ministry of Health to identify challenges and opportunities for establishing PVS, and synthesised my findings into recommendations for the development of a PVS strategy for Tonga. To be feasible, LF PVS must be designed for Tonga's unique systemic, organisational and operational environment; my proposed strategy consists of determining local risk level and context, and using this assessment to select from both active and passive surveillance methods.

This thesis also describes other public health experiences that have contributed to my training in field epidemiology. This includes six weeks of fieldwork in Tonga, where I assisted with a serosurvey investigating resurgence of LF following its elimination seven years prior. I also investigated a Salmonella Typhimurium cluster with Queensland Health's OzFoodNet team. Lastly, I contributed to other publications within the ODeSI team.

The work presented in this thesis demonstrates the role of applied epidemiology in public health decision-making in diverse settings across the Western Pacific region, from the Gold Coast to the Pacific Island Countries of Fiji and Tonga. Show more