Background and Aim

Listeriosis outbreaks are rare but high risk, particularly in regional settings where cases may be dispersed across multiple jurisdictions. Between March and April 2024, six confirmed cases of listeriosis were identified across the Loddon Mallee region. Early interviews suggested a shared food exposure, but confirming the source required large scale sampling across seven local government areas.
This investigation highlighted the importance of strong, preexisting partnerships with local councils. The presentation aims to share lessons to support preparedness and strengthen capability across the public health network.

Methods and Analysis

An Incident Management Team was established in late March 2024, involving public health, epidemiology, clinicians, local councils, the Department of Health, and regulators. Although epidemiological evidence pointed toward a common retail chain, the response depended on rapid, broad inspection and sampling capacity. Environmental health teams from seven councils were engaged within days. Established relationships, local knowledge, and shared protocols enabled efficient inspections, coordinated access, and consistent sampling. In total, 34 premises were inspected, and 196 food and 107 environmental samples were collected. Clinical, food, and environmental isolates underwent microbiological and genomic analysis.

Outcomes

Several food and environmental samples tested positive for Listeria monocytogenes, with genomic sequencing confirming a closely related strain across most cases. A product supplied by a single company was identified as the likely source, with evidence of cross contamination at retail outlets. Rapid council mobilisation across jurisdictions was essential in confirming the source and supporting regulatory action. No further cases occurred after April 2024.

Conclusion and Learning Objectives

This outbreak demonstrates that strong partnerships with local government are critical for complex foodborne investigations in Victoria. Following an after-action review, LMPHU shared key findings to support system wide improvement, strengthen preparedness, and avoid duplication.

Learning objectives:

1. Recognise the value of local government partnerships in outbreak response.
2. Identify strategies to enhance cross agency collaboration.
3. Apply lessons to strengthen regional and multi-jurisdictional preparedness.

Background and Aim:
In early 2024 approximately 7000-10,000 people attended a long weekend music festival in rural Victoria, Australia setting the stage for one of the largest shigellosis outbreaks seen in Australia. The outbreak was complicated by a high-risk festival setting, heatwave and extensive drug resistance. A major challenge to the initial outbreak response was the large number of potential transmission routes (such as unregistered staff kitchen, shared facilities, onsite drinking water filtration, swimming in agricultural dams) and the difficulties of timely data collection in a remote setting.
Methods and Analysis:
Routine notification of the outbreak was reported by local council to the local public health unit. Festival medics provided an initial case list of presentations for gastro symptoms, but data completeness was poor. To support rapid case identification, exposure assessment, and public health action across a dispersed cohort of up to 10,000 attendees, an active case finding survey was developed using REDCap.
Outcomes:
Active case finding allowed for detailed case information to be collected rapidly and helped inform a state-wide response. Within 11 days of outbreak notification passive surveillance had identified 8 laboratory confirmed outbreak associated notifications while 282 unique survey responses were received adding valuable intelligence. The identification of drug resistance had implications for clinical management and heightened the need for a rapid coordinated public health response. The epidemiological data suggested a likely point source in festival staff, with secondary person-person spread during the festival.
Conclusion and Future actions:
This outbreak demonstrates the challenges of data collection in remote festival settings and highlights the value of scalable active case finding data collection techniques. The outbreak also emphasises the importance of incorporating public health incident preparedness into mass-gathering planning and reinforces the need for collaboration between event organisers and local authorities to ensure adherence to health and safety guidelines.

Background and Aim
Global emergence of antimicrobial-resistant Shigella strains poses a major challenge for the control of shigellosis. This study aimed to describe national trends and sociodemographic characteristics of shigellosis cases in Australia between 2017–2024 to inform surveillance and interpretation of emerging antimicrobial resistance (AMR) patterns.

Methods and Analysis
Descriptive analyses of National Notifiable Diseases Surveillance System (NNDSS) data examined temporal trends; age and sex distribution; geographic patterns by remoteness and Index of Relative Socio-economic Advantage and Disadvantage (IRSAD); acquisition location (overseas, Australia, unknown); and laboratory characteristics (organism, subtype, testing method). Analyses were conducted using R version 4.5.1.

Outcomes
16,761 confirmed and probable cases of shigellosis were notified to the NNDSS between 1 January 2017–31 December 2024. Crude notification rates peaked at 12.4 cases per 100,000 in 2019, declined to a low of 1.8 per 100,000 in 2021 during the COVID-19 pandemic, and increased from 2022 onwards, returning to high levels by 2023–2024.
54.8% of notifications (9,191/16,761) were male. Median age was 32 years (IQR 13–48). Adults aged 20–49 years represented the largest proportion (7,964/16,761, 47.5%), followed by children aged 0–4 years (2,578/16,761, 15.4%). Of all notifications, 5,818 (34.7%) were overseas-acquired; 4,882 (29.1%) Australian acquired; and 6,061 (32.5%) unknown. Notification rates were highest in IRSAD decile 1 (178 per 100,000 population), followed by deciles 9 (116.6 per 100,000) and 10 (100.9 per 100,000).

Conclusion and Future actions
National notifications indicate substantial and evolving burden of shigellosis in Australia, including a post-pandemic resurgence in transmission.
Disproportionate impact among young children and key adult populations identifies potential priority groups for prevention. Variation by remoteness area and IRSAD decile highlights differences in notification distribution.
Planned analyses integrating Antimicrobial Use and Resistance in Australia (AURA) surveillance program Shigella data will strengthen the epidemiological findings by examining AMR patterns to inform surveillance priorities and support timely, targeted public health response.

Background and Aim
Hepatitis E is liver inflammation caused by hepatitis E virus (HEV). Genotypes 1 and 2 primarily infect humans and are common in countries with poor sanitation, while genotypes 3 and 4 are zoonotic in origin. In Australia, HEV infections are rare and generally associated with travel overseas. However, Australian acquired HEV-3 infections occur sporadically. In October 2025, an increase in Australian acquired HEV infections was identified and an investigation commenced.

Methods and Analysis
An outbreak case was defined as cases notified since 1 January 2025 with either an Australian or unknown place of acquisition and belonging to novel Australian HEV-3 subtypes Alpha or Beta on HEVnet sequencing. Outbreak cases were investigated using standard jurisdictional processes. A central database was established to collate and analyse investigation findings. Sequence data was shared with a single laboratory for national comparative analysis using the internationally standardised HEVnet protocol.

Outcomes
To 31 January 2026, nine outbreak cases were identified. All were male and the median age was 60 years (range 30-81 years). Seven cases were hospitalised and all survived. The Alpha subtype cluster included five cases (three from New South Wales, two from Victoria) of which three reported consuming banh mi containing pork liver; two from the same bakery. The Beta subtype cluster included four cases (two from Queensland and two from South Australia). Three out of four cases reported consuming liverwurst produced by the same manufacturer. No epidemiological links between the two subtype clusters were identified.

Conclusion and Future Actions
Australian acquired HEV-3 cases have increased in recent years. Limitations in testing methods make it difficult to identify sources of infection and control the broader public health risk. Inter-agency collaboration is required to establish one health surveillance mechanisms to better understand and respond to the risk of HEV infection in Australia.

Background and Aim
Shigella species and Entero-invasive Escherichia coli (EIEC) are related bacterial pathogens that can cause serious gastrointestinal illnesses and often have a similar clinical presentation. In early 2025, the Torres and Cape Public Health Unit identified a cluster of shigellosis notifications in a remote Aboriginal community in the Cape York region of Far North Queensland, prompting an outbreak investigation and response.
Methods and Analysis
Notified shigellosis cases were classified as confirmed or probable using the Australian National Surveillance Case Definition. Given initial low faecal testing numbers, a possible outbreak case definition was also developed based on clinical presentations to the local primary healthcare centre, with cases identified through review of clinical records, laboratory data, and hospital admissions. Environmental investigations assessed drinking water quality, food premises hygiene and sewage infrastructure. Community led health promotion and clinical education were implemented during the response to reduce bacterial spread throughout the community.
Outcomes
A total of 43 cases were identified between 1 January and 28 April 2025, including 14 probable cases polymerase chain reaction (PCR) positive for a gene common to Shigella and EIEC, and 29 possible cases. No Shigella was isolated on reflex culture, meaning no confirmed cases were identified. Cases were predominantly female (33/43, 77%), with a median age of 11 years (range 0-71 years). A total of 13/43 cases (30%) required hospitalisation, including two who were admitted to Intensive Care. Environmental investigations found compliant drinking water and food premises but identified a prior sewage leak as a potential contamination pathway during heavy rainfall.
Conclusion and Future Actions
While PCR has improved case and outbreak detection of Shigellosis in recent years, there are no diagnostic methods in use in Australia to identify EIEC when Shigella culture is negative. Culturally appropriate health promotion and ongoing collaboration with community stakeholders is essential to break down stigma around faecal testing and ultimately improve the management of severe gastroenteritis outbreaks in Aboriginal and Torres Strait Islander communities.
Aboriginal and Torres Strait Islander peoples’ health statement
The outbreak response was conducted in partnership with local staff and organisations who enabled culturally considered engagement that was able to be adapted to the needs of the community. Strong collaborative involvement of all parties was central to the success of the response, including Apunipima (the local Aboriginal Community Controlled Health Organisation), Aboriginal Health Workers, the Aboriginal Shire Council, local Environmental Health Officers, Aged Care facility staff, the women’s group and local state school. The willing engagement of local community members to support the response, foster health promotion messages and seek treatment early ultimately reduced ongoing local transmission and are credited with the outbreak drawing to a rapid close. The lead author is a Iamalaig and Kaantju women and hopes to deliver the presentation in person at the conference.

Background and Aim
Non-typhoidal Salmonella bacteria are an important global cause of gastrointestinal disease. In Australia it is estimated that salmonellosis costs approximately 140 million Australian dollars per year in illness, pain and suffering and other productivity losses. The Northern Territory (NT) of Australia is a sparsely populated tropical environment, with 31% of the population being Aboriginal Australians.

Methods and Analysis
We described the epidemiology of salmonellosis in the NT by analysing routinely notified salmonellosis cases diagnosed between 2005-2024. We performed descriptive, univariate and multivariate analyses. We used exact logistic regression to explore associations with serious disease (hospitalisation or death). We performed negative binomial regression analysis to explore associations with length of hospitalisation.

Outcomes
There were 9,628 salmonellosis notifications equating to a mean annual notification rate of 203 per 100,000 persons - the highest reported in the world; 51% of cases were male; 25.3% had serious disease (2,432 hospitalisations and 18 deaths); and 50% were aged <5 years. The most commonly reported serotypes were S. Saintpaul (1,125/9,628, 11.7%), S. Virchow (1,002/9,628, 10.4%) and S. Typhimurium (936/9,628, 9.7%). Aboriginal people were notified at 1.2 times (95% CI 1.1-1.2, p<0.001) the rate of non-Aboriginal people, were 3.7 times (95% CI 3.3-4.1, p<0.001) more likely to experience severe disease, and were hospitalised for 1.6 times longer (95% CI 1.5-1.8, p<0.001) than non-Aboriginal people. There was no difference in salmonellosis notification rates in 2005-2014 compared to 2015-2024; however, S. Typhimurium notifications decreased.

Conclusion and future actions
The tropical climate, abundant wildlife and contamination of the household environment with Salmonella contributes to high rates of salmonellosis in the NT. Credible interventions are needed to decrease the incidence of salmonellosis, particularly among young children exposed to contaminated tropical environments.

Background and Aim

Large regional events pose complex public health risks, particularly where sanitation, infrastructure, and medical capacity are limited. In March 2024, a large gastroenteritis outbreak at the Esoteric Festival highlighted opportunities to strengthen pre-event planning, risk assessment and environmental health oversight. While the outbreak was contained, it revealed the need for a more consistent, preventative approach to mass gathering safety. This abstract outlines how the Loddon Mallee Public Health Unit (LMPHU) collaborated with local councils and emergency management partners to embed outbreak learnings into planning systems and reduce future risk.

Methods and Analysis

LMPHU facilitated structured multi-agency debriefs with local councils, environmental health teams, emergency management, the Department of Health and the Local Public Health Unit network. Key themes were consolidated across agencies, including sanitation risks, extreme heat impacts, food safety controls, on-site medical capacity, and communication pathways. LMPHU then provided formal recommendations to Buloke Shire Council to incorporate these insights into the 2024 Community Emergency Risk Assessment (CERA) review. This involved jointly assessing mass gathering risks, identifying system gaps and developing practical, prevention focused recommendations for event organisers and regulatory partners.

Outcomes

The CERA review strengthened governance for future events, provided council expectations for organisers and improved risk mitigation measures. Key changes included integrating extreme heat and communicable disease risks into event assessments, enhanced oversight of sanitation and food safety infrastructure, formalised communication and incident management pathways, and clearer requirements for on-site medical capacity. Embedding outbreak insights into an established emergency management framework ensured consistent adoption across agencies and reduced duplication. As a result, the scheduled 2025 event did not receive local government approval, because the planning permit failed to meet the updated requirements.

Conclusion and Future Actions

This work demonstrates how local public health units can translate outbreak response into long term prevention by partnering with councils and emergency management to influence planning systems. Future actions include extending this approach across other LGAs, strengthening accountability for event organisers and continuing to integrate public health intelligence into emergency management processes.

Learning Objectives

1. Understand how outbreak insights can inform systemic improvements in event planning.
2. Identify approaches for integrating public health learnings into emergency management frameworks.
3. Apply prevention focused strategies to reduce health risks at future large events.