Hepatitis B is a major health problem in vulnerable communities in Australia. An increase in newly acquired Hepatitis B virus (HBV) notifications in metropolitan Perth was observed in early 2023-24, triggering an outbreak investigation. Notifications of newly acquired HBV were reviewed, and genomic investigation conducted to determine if the HBV cases were related and identify risk factors.

A descriptive study of newly acquired Hepatitis B cases notified between August 2023 and August 2024. Data for the epidemiological investigation was derived from the Western Australian Notifiable Infectious Diseases Database (WANIDD) and the Hepatitis B REDCap database at Boorloo (Perth) Public Health Unit to analyse demographics, risk factor identification, the timing of disease onset and links between cases. Genotyping and whole genome sequencing was conducted at the state’s reference laboratory, PathWest.

There were 24 cases included in this investigation. Most cases were over 30 years old (n=19, 79%), with similar numbers of male and female cases, and only 17% (n=3) were fully vaccinated. Aboriginal cases were over-represented (n=6, 25% compared to 2% in the population). The most common risk factor reported was unprotected casual sex (n=18, 75% of cases), followed by born overseas (n=8, 33%) and intravenous drug use (33%). Sequencing was possible for 20 cases (83%). Of the genotyped cases, 12 (60%) were identified as subgenotype A2. Whole genome sequencing (WGS) indicated that there were two clusters of A2 cases (3 cases and 2 cases), and one cluster of B3 cases (2 cases) that were genomically identical.

There was an unexpectedly high number of HBV A2 cases identified via sequencing; however, many cases were not linked epidemiologically or genetically. This HBV WGS investigation is one of the first in Australia and demonstrates the utility of WGS when outbreaks are suspected but where there are few direct epidemiological links.

Background: Hepatitis A, an acute enteric illness of faecal-oral transmission, is not endemic to Australia. On 2 September 2024 Western Public Health Unit (WPHU) was notified of a case of hepatitis A in a five-year-old female who had not travelled overseas. The child attended the same primary school junior campus as a case notified three weeks earlier in a six-year-old female who acquired infection whilst visiting family in an endemic country and subsequently attended school whilst infectious. WPHU led a response to investigate the outbreak and implement control measures.

Methods: Outbreak cases were confirmed or probable cases of hepatitis A (per CDNA SoNG) with a symptom onset from 12/08/2024 and an epidemiological link to the school or another outbreak case.

Investigation included case interviews, environmental assessment of the school, and laboratory investigations including genotyping. Management included communication with the school community, infection prevention and control interventions, and a vaccination clinic to provide post exposure prophylaxis (PEP) for identified contacts including household contacts of students.

Results: Including the index, five cases were linked to the outbreak: four students and one parent of an unaffected child. Cases were identified in three of the five junior campus classes. All cases attended the campus during the index case's infectious attendance period, including the adult case who attended two on-campus events during this period.

128 children and 155 adults (approximately 67% of eligible contact population) received hepatitis A vaccine PEP via the pop-up vaccination clinic, likely meeting the herd immunity threshold. No cases were acquired following the interventions. Whole genome sequencing confirmed all five cases to be genomically linked.

Conclusions: The response to this outbreak in a primary school setting demonstrated the importance of clear, proactive communication, thorough environmental assessment and IPC interventions, and timely mass vaccination to prevent further propagation of cases.

In response to emerging diseases and the growing need for timely public health interventions, the Liverpool Public Health Unit (PHU) in South Western Sydney District (SWSLHD) implemented innovative communication strategies. Throughout 2024, SWSLHD observed significant spikes in notifications of cryptosporidiosis and pertussis. Cryptosporidium notifications in the three months ended 31 March 2024 ("Q1 24") increased 1,439% over the three months ended 31 March 2023, with 200 notifications in Q1 24 compared to 13 notifications in Q1 23. Pertussis notifications in the three months ended 30 September 2024 ("Q3 24") increased 4,268% over the three months ended 30 September 2023 ("Q3 23"), with 1,354 notifications in Q3 24 compared to 31 notifications in Q3 23. Following these increases, Liverpool PHU adopted a targeted survey aimed at identifying infection sources and ensuring efficient follow-up. This proactive strategy resulted in an over 60% response rate, significantly enhancing the identification and management of cases.

The survey method has since been expanded to address other public health concerns, such as foodborne illness outbreaks, highlighting its versatility and adaptability in managing various disease outbreaks. A key advantage of this system is the integration of secure survey forms, replacing traditional methods of phone calls, fax and email for communicating sensitive health information. This transition has improved confidentiality when following up on cases such as syphilis, particularly when liaising with health professionals in Sexual Health Clinics or general practices.

This innovative communication strategy has proven to be highly effective in facilitating rapid case follow-up, identifying sources of infection, and fostering public engagement in health initiatives. These advances underscore the potential for technology-driven solutions in enhancing public health responses and improving outcomes during disease outbreaks.
By integrating these modern communication tools, Liverpool PHU exemplifies how health services can adapt to evolving challenges, ensuring timely and effective public health interventions.

Objectives: This presentation describes the outbreak investigation and public health response to a cluster of mpox cases in Southeast Queensland in 2024; and to provide recommendations for the control of future outbreaks of mpox. Design: The admission of an mpox case to a Queensland hospital in May 2024 precipitated the coordinated response from two metropolitan public health units. A prospective cohort study design was used to follow up attendees of an intimate group event over a 21-day period. Main outcome measures: Relative risk was determined for developing infection after attendance at the group event, when taking into account, the level of vaccination against monkeypox virus (MPXV). Results: Transmission of MPXV occurred exclusively among high-risk contacts, and no transmission was observed to medium, nor low risk contacts. Laboratory investigations revealed all cases in this outbreak were of human MPXV clade 11b. Study findings suggested that complete vaccination against mpox virus was a protective factor against development of mpox (Relative Risk=0.33, 95% CI: 0.06-1.88) compared with partial or no vaccination, after attendance at the high-risk exposure event. The investigation demonstrated that building trust with event attendees and their contacts was crucial to the attainment of case histories and assisted greatly in the overall public health response. Conclusion: Learnings from this investigation suggest there is less urgency for follow-up of household contacts and other medium and low-risk contacts of mpox, compared with high-risk contacts. A huge thanks is owed to the extensive group of public health workers in the Southeast Queensland area for carrying out this comprehensive public health response.

An outbreak of salmonellosis occurred in August 2024 after consuming wild hunted kangaroo in a remote area of the Northern Territory (NT), Australia.

We conducted an outbreak investigation via telephone and face-to-face interviews, using a standardised questionnaire that recorded symptoms and exposures to foods and activities prior to onset of symptoms. A confirmed outbreak case was defined as anyone with laboratory confirmed Salmonella Muenchen infection who was part of a group of people who shared meals on 25–26 August 2024. A probable outbreak case was defined as anyone who was part of a group of people who shared meals on 25–26 August 2024 and subsequently experienced diarrhoea, in the absence of a laboratory test.

Of the seven members of the group who shared meals, all became ill (attack rate 100%); three were confirmed cases and four were probable cases. The median age was 32 years (range 23–65 years); six (86%) were male. The median incubation period was 24 hours (range 6–30 hours). The most commonly reported symptoms were diarrhoea (100%, 7/7) and abdominal pain (86%, 6/7). Two cases were admitted to hospital, both for an overnight stay; all recovered.

All seven cases consumed the same meal – a single, locally hunted and butchered kangaroo. Contamination likely occurred due to unsafe butchering, storage, transportation and insufficient cooking of the meat. This outbreak highlights the risks of contamination of game meat (in this case kangaroo) with Salmonella. Those preparing hunted meat should wash hands and knives regularly while butchering an animal to avoid contamination; should store butchered meat below 5 °C to avoid bacterial growth and cook foods thoroughly to kill microbes. We estimate that the cost to society of this outbreak was 9,810 Australian dollars.

Background

Measles is a highly contagious viral, airborne disease which typically presents with high fever, cough, conjunctivitis and a maculopular rash. While no longer endemic in Australia, imported cases do occur. A single case of measles is a public health emergency requiring rapid contact tracing to prevent further cases. In January 2025 a returned traveller with measles was notified to the Centre for Disease Control (CDC) in Darwin, Northern Territory (NT); the first case in NT since 2019.

Methods

A weekend outbreak team was formed to follow national public health response guidelines. We interviewed the case to determine travel history, infectious period and potential contacts and provided isolation advice.
A Research Electronic Data Capture (REDCap) database recorded contact details, vaccination status and past infection history. Telstra Integrated Messaging was used to send text messages to contacts, asking them to telephone CDC. A REDCap questionnaire was administered to determine susceptibility to infection, identify further contacts and determine appropriate public health action. Eligible contacts were given either measles-mumps-rubella (MMR) vaccine or normal human immunoglobulin (NHIG) to prevent measles infection. Staff overtime hours and cost were calculated.

Results

We identified 164 contacts; 155 (94%) were successfully contacted; 9 (5%) were lost to follow up but fully vaccinated. Five contacts (3%) received the MMR vaccine, one person received NHIG. Two contacts were symptomatic and tested for measles, both tested negative. The contact tracing was completed by 8 staff over 12 hours on a weekend. We calculated the human resource cost for this outbreak response to be approximately $7,200.

Conclusion

This outbreak response highlighted vaccine effectiveness and that a rapid, co-ordinated response was critical in preventing transmission. The use of REDCap as a contact tracing database allowed for an effective and cost-efficient public health response.

In January 2025, the Hunter New England Public Health Unit (HNEPHU) investigated an outbreak of invasive meningococcal disease (IMD) amongst residents of a residential aged care facility (RACF) in regional NSW. Two residents from the same wing of the facility were diagnosed with IMD six days apart. Both were serogroup Y and genomically identical on whole genome sequencing. Despite residing in the same wing, the second case was not identified as a close contact of the index case during a thorough risk assessment.
Outbreak management and a coordinated response by the HNEPHU, facility and primary health care providers involved provision of clearance antibiotics to all residents in the affected wing and staff members identified as high-risk. Vaccination was offered to all residents of the facility and identified high-risk staff. Messaging was provided to residents, resident’s representatives, and staff at information sessions, and the community was alerted through a media statement. Finally, enhanced surveillance and infection prevention and control (IPC) measures were instituted to reduce ongoing risk. The outbreak was closed four weeks after the last case and no further cases were identified.
To our knowledge, this is the first IMD outbreak in a RACF reported in Australia and demonstrates important learnings. Firstly, leveraging outbreak management knowledge and skills refined by RACF staff during the COVID-19 pandemic proved to be effective in facilitating: evolving complex risk assessments; communication with residents, families and staff; and timely implementation of infection prevention and control measures.
Secondly, this outbreak identified several key strategies used by HNEPHU that supported a timely and efficient response despite being remote from the RACF.
We will discuss how these learnings can be adapted and used to better manage infectious disease outbreaks in RACFs, particularly in rural and regional areas of Australia.

Background: Tuberculosis (TB) is a global public health problem and can present unique challenges where community outbreaks occur. We report a prolonged outbreak of TB with an unusual MPT64 negative status, first detected in North Queensland in 2017-2018.
Methods: A retrospective epidemiological and laboratory investigation (including whole genome sequencing, WGS) into potentially linked cases was undertaken. The aim of this study was to describe the outbreak, identify possible transmission settings and outline the challenges in the outbreak response.
Results: WGS provided evidence of serial transmission between 3 or more cases, fulfilling the TB outbreak definition. Between 2002-2023, a total of 47 outbreak cases were identified; 44 were closely linked by WGS and 3 were epidemiologically linked. Cases were all adults with a median age of 42 years (range 18-68 years). 64% of cases were male and 87% were First Nations Queenslanders. A median of 2 cases per year (range 0-6) were identified. More cases occurred in the northern Queensland regions of Cairns (0-4 per year) and Townsville (0-2 per year); however, cases were dispersed across 6 health areas during the 21-year period. A cluster that had been earlier identified in 2011-2015 was discovered to be a subset of this outbreak. The public health response focussed on active case finding and follow up of their close contacts as per national guidelines. Contact tracing was expanded in high-risk settings, such as homeless shelters.
Conclusion: The public health response to this outbreak has been challenged by prolonged transmission and geographically dispersed cases. WGS confirmed the outbreak and informed the extent of cases. This outbreak highlights an opportunity to reconfigure and partner TB prevention efforts with local communities for a broader approach to reduce TB transmission.

In 2024, high pathogenicity avian influenza (HPAI) H7 was detected in three Australian jurisdictions. In NSW, HPAI H7N8 was detected in birds in two commercial properties and four private properties in the Hawkesbury region. Given the clinical symptoms and detections, the virus likely spilled over from commercial properties to domestic birds within the established biosecurity zone.

NSW Department of Primary Industries and Regional Development (DPIRD) led the NSW outbreak response, supported by NSW Health.

NSW Health risk assessed people exposed to the infected poultry and material, facilitated fast-tracked testing for those who developed symptoms, and recommended seasonal flu vaccination and antiviral prophylaxis and advice. Risk assessment tools were adapted to consider the varying ways and settings people interact with domestic, commercial and wild birds. Similarly, a scalable contact management system was needed to better address the types of exposures.
Of 62 contacts assessed, 25 were considered high risk and monitored for 10 days via SMS survey. None were positive for influenza A virus. There was nil uptake of antiviral prophylaxis.

Challenges included contacts voicing concerns about influenza vaccine effectiveness and reflecting a potential lack of trust in vaccine recommendations and of public health control measures.

The outbreak identified the need for improved public health guidance, and targeted prevention communication to people at greater risk, including those in the poultry, biosecurity, wildlife, and environment industries.

The spillover of the virus into private residential settings presented new challenges, such as the adaptation of the risk assessment tool to consider how people interact with birds and a scalable contact management system to facilitate public health management of contacts in future outbreaks.

Lessons from the response have been incorporated into revised national guidelines for avian influenza for public health units. These lessons are valuable to inform preparations for the potential incursion of H5N1.

Background

Foodborne Vibrio parahaemolyticus (Vp) outbreaks are uncommon in Australia. A marine heatwave (MHW) was observed along Australia’s east coast in January 2024. In February 2024, NSW Health commenced an investigation into an increase of Vp foodborne infections in residents of other jurisdictions who had visited NSW.

Methods

Active case finding was conducted by requesting NSW laboratories to report identification of Vp in stool samples from 1 January 2024, and requesting other jurisdictions notify NSW of any cases with exposure in NSW. A descriptive case series was undertaken using a standard questionnaire. An outbreak case was defined as Vp isolated from stool, in a resident of NSW or VIC or ACT, or person who had travelled to NSW within their incubation period, with a specimen collection date on/after 9 January 2024, and the absence of travel overseas within 7 days prior to onset. Trace-back, food and environmental sampling were conducted by NSW Food Authority. Whole genome sequence analysis was completed for all cultured samples.

Results

Thirty-seven outbreak cases from four different jurisdictions were identified between 9 January and 27 March 2024. Thirty-three (89%) cases reported eating oysters during their incubation period. Trace-back identified the source of oysters consumed by cases as two growing areas in southern NSW. Testing of oyster meat samples yielded four positive cultures. Genomic analysis identified a cluster present with fourteen clinical and one oyster isolate. Closure, product withdrawal, sampling and monitoring, cool chain verification and relay requirements were control measures implemented prior to reopening of oyster growing areas.

Conclusion

Vp outbreak cases were associated with oyster consumption from two growing areas in NSW with a concurrent MHW occurring favouring the proliferation of Vp. MHW are predicted to become more frequent due to climate change, influencing Vp virulence and diversity. Vp outbreaks may consequently increase in frequency.

Background
A large outbreak of avian influenza occurred in poultry farms in Victoria, Australia in 2024. Risk assessment of the 212 people exposed to avian influenza (“contacts”) on affected properties identified 172 contacts as eligible for post-exposure prophylaxis or treatment with influenza antivirals and seasonal influenza vaccination. Seasonal influenza vaccination is recommended for poultry workers during an outbreak of avian influenza; it does not protect against avian influenza, however could help prevent genetic reassortment between the viruses and emergence of a potentially pandemic subtype. Influenza antivirals were recommended for high-risk contacts (prophylaxis) and any symptomatic contacts (treatment) to reduce infection risk and disease severity.
Local primary care providers and health services facilitated provision of antivirals and vaccination free of charge. Despite these efforts, low uptake of vaccination and antivirals was observed among contacts.
Aim
The study aims to understand the enablers and barriers to antiviral and seasonal influenza vaccine uptake among contacts exposed to avian influenza.
Methods
A REDCap survey has been developed to explore factors influencing uptake and access to vaccination and antivirals. The survey was sent to all eligible contacts (N=172) via SMS. This included a translated version (Bahasa Indonesia) of the survey and SMS for 22 contacts.
Results
Preliminary analysis suggests factors such as perceived low risk of avian influenza, concerns about side effects, and difficulty accessing healthcare due to work constraints may have contributed to low uptake of antivirals and vaccination. Detailed results from this ongoing study will be presented.
Conclusion
Enhanced education on the risks of avian influenza could improve the uptake of vaccination and antivirals among high-risk groups. Further investigation is needed to explore factors influencing the uptake of these preventative interventions among workers exposed to avian influenza during outbreaks.