Epidemiology in the age of COVID-19: Relying on basic epidemiological tools to assist and inform public health action

Abstract

Global pandemics often exert an extraordinary burden on local public health systems and health care providers. As epidemiologists worldwide step up to the challenge, they must rely on the basic tools of field epidemiology to perform their duties, which can be summarised by the four core competencies specified by the MAE: Outbreak investigation, surveillance evaluation, epidemiological research, and data analysis. The present thesis addressed these four competencies and discussed the tools implemented for each. The thesis covered a range of different diseases and health events in addition to COVID-19, to represent the range of topics an epidemiologist must be prepared to tackle at any time, and especially in the midst of a global pandemic. Placed at the Communicable Disease Control Branch (CDCB) at SA Health, one of my earliest MAE experience involved leading a cryptosporidiosis outbreak investigation in a regional town in South Australia. As lead investigator my first responsibility was to ensure the implementation of appropriate public health action to protect the community. Initial hypothesis generating interviews provided sufficient information to identify a likely source of infection, informing the department on the type of health measures needed to prevent further transmission. In addition to the concepts of person, place and time, a retrospective cohort study was conducted, and the Bradford Hill criteria discussed. I also performed an evaluation of the CDCB's shigellosis surveillance system, with a focus on its ability to detect and identify multi-drug resistant (MDR) cases. For this task I utilised a mixed methods approach that included a quantitative analysis of the shigellosis surveillance data recorded by the CDCB for the past five years, as well as a qualitative survey of a small number of key stakeholders, including laboratory representatives. For this project I followed the CDC surveillance evaluation guidelines and chose system attributes appropriate to the disease. All findings and recommendations resulting from this evaluation were shared with the department. For my epidemiological research project I had the opportunity to delve into non-communicable epidemiology by assisting the Prevention and Population Health Branch (PPHB) at SA Health, regarding the South Australian Cancer Registry (SACR). Here I was tasked to review a quality assurance exercise designed to improve the completeness of Aboriginal and Torres Strait Islander identification in the SACR. This involved reviewing information obtained from a data linkage project already conducted by a third party and assess the efficacy of different algorithms to derive results on Aboriginal and Torres Strait Islander status from the linked data. In this investigation I used standard cancer health indicators to compare estimates across the different algorithms, as well as comparing these with available Aboriginal and Torres Strait cancer data from other jurisdictions. Due to the lack of reliable gold standards for this type of procedures, an approach was developed, and its limitations discussed. For my final chapter I conducted data analysis on COVID-19 cases in South Australia. The purpose of this study was to determine differences in the demographics and disease severity risks between cases whose infection could be traced to a cruise ship, and those who did not. Aspects such as gender and age distributions were compared between these two populations, as well as number of hospitalisations, intensive care unit admissions and comorbidities. Findings obtained in this investigation highlighted the need to protect cruise ship passengers from a range of pathogens, including COVID-19, and proposed recommendations to better prepare public health systems to the demands involved in the quarantining of cruise ship travellers.