Epidemiology of foodborne and emerging infectious diseases in Australia, 2014 to 2015

Abstract

My placement was with the Zoonoses, Foodborne and Emerging Infectious Diseases section in the Office of Health Protection at the Australian Government Department of Health during 2014-2015. I focused on the following five projects.

I described the epidemiology of bacterial toxin mediated foodborne outbreaks in Australia and identified risk factors and risk groups, from an analysis of outbreak data recorded from 2001 to 2013. The main risk factor for bacterial toxin mediated foodborne outbreaks is temperature abuse (storage between 4C and 60 C) of solid masses of foods, such as lasagna. Residents of aged care facilities were the group at highest risk of illness and death from bacterial toxin mediated foodborne outbreaks. Few outbreaks were identified with food prepared at home.

As part of the national response to the large outbreak of Ebola virus disease (EVD) in West Africa (2014-2015), a national surveillance system was established to enable reporting and to provide information to jurisdictions to assist monitoring of travellers at risk of contracting EVD. I conducted an evaluation of this system. The system was considered useful and achieved its aims; however a coordinated central, online database would improve reporting and ease of use.

Culture independent diagnostic testing (CIDT) for bacterial causes of gastroenteritis is becoming commonly used in pathology laboratories in Australia. These tests are rapid, cheap and require less technical expertise than traditional culture based laboratory tests. However, these tests do not provide the subtyping information required for public health surveillance, including outbreak detection. For the time being, laboratories are continuing culture in addition to CIDT. My project documents this transition in Queensland.

In May 2014, three cases of bacteraemia caused by Ralstonia species were diagnosed in South Australia. The only common exposure was propofol, a sedative. An investigation into the cause of this cluster of cases was led by the Therapeutic Goods Administration (TGA) as the agency responsible for the regulation of propofol. Additional cases were identified from Queensland (four cases), and Victoria (one case). I was part of the epidemiology team assisting and advising the TGA. The investigation incorporated evidence from the case series, molecular analysis of isolates (including whole genome sequencing), assessment of causal association and expert consultation through the Delphi method. The cases of Ralstonia bacteraemia were determined to be associated with at least two separate exposures. Cases in Queensland were linked to contaminated bottled water, while cases in South Australia and Victoria were associated with propofol. The mechanism of contamination of the propofol was unable to be determined.

During a multi-jurisdictional investigation into an outbreak of hepatitis A associated with consumption of frozen mixed berries in 2015, a national case control study was conducted. I assisted OzFoodNet Queensland with interviewing controls and conducted a sub-analysis of cases and controls from Queensland. Frozen mixed berries were the only food exposure with a statistically significant association with illness, supporting the implication of frozen mixed berries as the source of the outbreak, as indicated by traceback and microbiological evidence. Show more