Investigating diseases of public health importance - Victoria, Australia

Abstract

In this thesis, I present the projects and activities I have undertaken as a Master of Philosophy in Applied Epidemiology (MAE) Scholar in Victoria. Between February 2013 and December 2014, I was placed with Communicable Disease Epidemiology and Surveillance at the Victorian Department of Health and the Epidemiology Unit at the Victorian Infectious Diseases Reference Laboratory (VIDRL). Through these placements I experienced the day-to-day activities of a public health unit, as well as the applied public health research environment provided in a reference laboratory setting. During my MAE I analysed data to examine the relationships between antimicrobial resistance patterns in Shigella isolates and risk factors for shigellosis. I have found that location of travel is a possible marker of antimicrobial resistance patterns in shigellosis cases and found significantly elevated levels of ciprofloxacin resistance amongst travellers returning from India and their contacts. This project also highlights the prominence of periodic outbreaks amongst men who have sex with men (MSM) in driving shigellosis case numbers in Victoria and indicates a reconsideration of Australian treatment guidelines for shigellosis may be needed. As a result of this project, I also communicated with selected general practitioners and the community to increase awareness of an outbreak of shigellosis amongst MSM in 2014. My epidemiological project examined the effects of restriction criteria and covariate inclusion in the case-test negative design to estimate seasonal influenza vaccine effectiveness (VE). Using six years of data from the Victorian General Practice Sentinel Surveillance System I defined an optimum logistical regression model for this new, but growing, method of analysing sentinel influenza surveillance data to provide rapid annual estimates of influenza VE. I also report supporting evidence that repeated seasonal influenza vaccination in both the current and previous year may be less effective at preventing influenza than vaccination in only the current season. I report on two outbreak investigations. The first was a cohort investigation into an outbreak of gastroenteritis of unknown aetiology following a catered lunch. Attendees at the lunch were divided into three groups representing a standard meal in low, middle and high-income countries. I believe the source of illness to be a dahl curry served as part of the low-income country meal and stored in a hot box prior to serving. We have communicated potential improvements in food safety practices the to prevent further outbreaks. The second outbreak is a descriptive investigation of a Salmonella Typhimurium phage type 64 cluster identified in Victoria in 2013. I evaluated national hepatitis A surveillance in Australia, focused on detection of common-source multi-jurisdictional outbreaks. I consider the potential to enhance surveillance using nationally collated genotyping, sequencing and standardised exposure data. Finally, I present two teaching activities conducted during my MAE; a teaching session on selection bias and a lesson from the field introducing directed acyclic graphs I prepared for my fellow MAE2013 cohort. This thesis provides an account of my MAE experience, fulfils the requirements of the program and outlines the contribution my work has made to public health in Victoria.