Background
Global health impact of climate change is reshaping infectious disease ecosystems, spreading infectious disease regions, and increasing human susceptibility. Japanese encephalitis (JE)—now entering its fourth season of domestic endemicity—highlights this evolving health-risk landscape, as warmer weather and flooding create ideal conditions for mosquito breeding. In response, the once exotic JE vaccination swung from an expensive option for intrepid international travellers to a government-funded domestic disease prevention strategy targeting people in the newly endemic JE-affected areas of South-eastern Australia. Maintaining vaccine uptake, initially hampered by global supply shortages, naïve local immunisation workforce and uncertain community acceptance, is critical as local transmission and emergent clinical cases continue.

Methods
Safe vaccination was supported through self-paced eLearning modules developed to rapidly upskill and bolster Victoria’s immunisation workforce in the public health response. Adverse events were captured through active and passive reporting to enhanced surveillance systems, calculated as reporting rate per 1,000 doses recorded in the Australian Immunisation Register.

Results
Over 1,000 health professionals completed eLearning within 3-months, enabling timely communication of evolving clinical advice, program changes and expansion of eligible risk cohorts.

JE vaccination in Victoria has seen a 7-fold increase from a pre-outbreak (2016–2021) average of 2,280 doses-per-year to over 48,900 outbreak doses delivered since 2022, with live chimeric Imojev® the dominant brand. Notified adverse events (rate 0.4 per 1,000 doses) were mostly mild with no specific safety signals observed. However, seven reports indicated vaccine administered in contraindication to immunocompromised persons, fortunately with no detrimental outcome.

Conclusion
Australia’s domestic JE vaccination program demonstrates agility and flexibility crucial for public health response amidst climate-change driven shifts in vector and disease epidemiology. Ensuring effective immuniser education—including brand-specific contraindications and undertaking adequate patient questioning—is essential to minimise avoidable risks and encourage vaccine uptake in an otherwise safe vaccination program.

Background: Within Australia, Buruli ulcer has traditionally been limited to defined areas of Victoria, Northern Territory and Northern Queensland. Evolving evidence suggests that the causative organism, Mycobacterium ulcerans, likely transmits from possums to humans via mosquitoes. In 2023 NSW Health was alerted to a Buruli ulcer case in a NSW resident without travel to known endemic areas. The condition was not notifiable in NSW at the time.

Methods: Enhanced case finding was instigated to identify any further local cases. Laboratory data was used to review Buruli ulcer cases in NSW residents from 2006-2023, which were examined for evidence of travel to endemic areas. Where possible, sequencing was sought for cases determined to be NSW-acquired. Possum faecal surveys were also undertaken in the relevant area to investigate the presence of M. ulcerans. Local community and clinical alerts were released to highlight the emerging risk and support early case identification.

Results: In 2023, two additional historical cases were identified in NSW residents without travel to known endemic areas. These first three cases occurred between 2021-2023 in Bateman’s Bay. Two cases’ isolates were sequenced and found to be highly related but distinct from Victorian sequences, supporting NSW acquisition. Possum faecal surveys in Bateman’s Bay also identified M. ulcerans. In early 2025, a fourth case was identified 30km away from the previously identified cases. This was in a geographically distinct area, separated by bushland and bridges that cross a river and bay area.

Conclusion: Buruli ulcer can be acquired in a discreet area of NSW. Our understanding of the distribution and transmission pathway is evolving. Increasing awareness of the presence of M. ulcerans in NSW among clinicians is paramount to ensuring consideration in differential diagnoses. Likewise, increasing vigilance against mosquito-borne disease among residents of, and visitors to, the NSW South Coast is important.

From Herd to Human: Lessons from Containing a Q Fever Outbreak in Gippsland

Background:
Gippsland is a rural region in southeastern Victoria where dairy farming and agriculture are key industries. Q fever, caused by Coxiella burnetii, is a zoonotic disease primarily transmitted through inhalation of contaminated aerosols from livestock. From 2024-25, the Gippsland Region Public Health Unit (GRPHU) managed a large Q fever outbreak among individuals associated with three interconnected goat farms.
Process:
The outbreak investigation identified 22 confirmed cases among 57 at-risk individuals (attack rate: 38.6%). Active case finding detected additional undiagnosed cases among farm workers and household contacts. Of the confirmed cases, 21 (95.5%) cases were symptomatic, with five (22.7%) requiring hospitalisation. Two-thirds were male, with a median age of 29 years (range: 19–56). No workers had prior vaccination for Q fever. WorkSafe conducted site assessments and Agriculture Victoria (AgVic) provided livestock movement data. GRPHU arranged Q fever vaccination for six individuals through local GP clinics.
Analysis:
This outbreak underscored challenges in coordinating a One Health response, balancing public health and occupational health priorities, and addressing gaps in vaccination and prevention. Delays in serological and PCR testing complicated case identification. Communication barriers between public health authorities, farm managers, and affected individuals hindered risk messaging and response coordination. Lack of clarity of roles and processes across human, occupational, and animal health agencies added complexity to response efforts. Preventive strategies, including PPE recommendations and vaccination promotion, were impacted by logistical and cost concerns.
Outcomes:
The outbreak highlighted the need for improved communication and coordination between human and animal health agencies to strengthen One Health responses. Enhanced surveillance protocols and better integration of occupational health into farm biosecurity are needed to mitigate future outbreaks. Expanding access to and promotion of Q fever vaccination for high-risk workers should be a priority. Policy discussions are necessary to explore stronger preventive measures, including potential vaccination requirements for high-risk industries.

Background: Encephalitis is inflammation of the brain parenchyma with heterogenous aetiology and presentation. In children, it often leads to adverse neurological outcomes. The Australian Childhood Encephalitis (ACE) study is a multi-centre prospective cohort study that aimed to describe the clinical features and long-term outcome of all-cause childhood encephalitis in Australia. It was undertaken through the Paediatric Active Enhanced Surveillance (PAEDS) network, and transitioned from a grant funded cohort study (2014-2018) to public health surveillance in 2019.
Methods: Cases of suspected encephalitis were actively identified from 5 paediatric tertiary hospitals 2013 to 2018 , then expanded progressively to 8 hospitals from 2019. An expert panel categorised cases into aetiological subgroups. Under the cohort study, follow-up was conducted at discharge and 12 months using the Liverpool outcome score for encephalitis as the primary outcome. Univariate logistic regression was used to determine predictors of adverse outcome, and a multivariate logistic model constructed. Additionally, we compared causal distributions across sites from the cohort period (2014-18) and subsequent surveillance period (2019-).
Results: From the cohort study (2013-18), of 724 suspected cases identified, 408 were confirmed as having encephalitis (58% infectious, 23% immune mediated, 19% of unknown aetiology). Recovery was incomplete in 58% of children at 12 months. Children with infectious encephalitis presented younger and showed divergent outcome progression from discharge to 12-month follow-up. Immune mediated encephalitis showed improved neurological outcome at 12 months relative to discharge. Several clinical and aetiological features predicted worse neurological outcomes at 12 months in a multivariate model. Since 2019, following transition to surveillance only, of 1027 suspected cases identified, 669 were confirmed as having encephalitis (59% infectious, 24% immune mediated, 16% of unknown aetiology).
Conclusions: Encephalitis in children results in a considerable ongoing disease burden with clinical features and outcome differing based on disease aetiology. Neurological deficits may evolve over time and close monitoring of children for at least 12 months is warranted. Surveillance causal distributions closely resemble those identified in an earlier cohort study.

Dengue is a vector borne viral infection which can become severe or fatal. Dengue rapid tests (DRT), a point of care test which can detect non-structural protein 1 (NS1) antigen, immunoglobulin G and immunoglobulin M were used to detect and respond to a dengue outbreak in a remote setting.
The Torres Strait is in Far North Queensland, previous outbreaks of dengue in the region have been associated with imported dengue cases arriving from Papua New Guinea. In November 2024, the Masig Island Primary Healthcare Centre in the Torres Strait reported seeing four patients with similar symptoms: fever, myalgia and headaches. Three cases were NS1 reactive indicating recent infection, and with no overseas travel reported, it was determined that this was a local outbreak of dengue.
Whilst confirmatory laboratory testing was collected, a public health response was initiated immediately. Consultation with local leaders and community occurred and a response team travelled to Masig Island within 48 hours of the rapid test results. The response included vector control, active case finding and health promotion. The early detection of dengue allowed the vector control team to rapidly commence treatment and eliminate infected mosquitoes which prevented transmission of dengue virus to other residents. Active case finding identified four more cases, with a total of eight cases in the outbreak. Laboratory test results came five days after the rapid diagnostic test results.
The DRT was an acceptable and easy-to-use test for the clinical staff and enabled a rapid response in a remote setting. The community supported the rapid public health response which enabled the prompt end of the dengue outbreak. The use of point of care tests such as the DRT in a remote setting can provide same day results and prevent delays in appropriate public health responses.

Introduction:

Chikungunya virus (CHIKV) is a threat to public health and a risk for travellers to endemic countries. Typical acute symptoms include fever, arthralgia, myalgia, fatigue, and headache. Debilitating arthralgias may persist for months or years. We report aggregated safety and immunogenicity data from five clinical trials for a CHIKV virus-like particle (VLP) vaccine, which has been approved for use by the US FDA in February 2025.


Methods:

To date, the CHIKV VLP vaccine development programme has included three phase 2 and two phase 3 trials across multiple sites in the US, which enrolled participants 12 to 95 years of age. Participants received a single dose of CHIKV VLP vaccine or placebo. The safety population included 3141 vaccinated and 675 placebo participants from five trials and the immunogenicity evaluable population included 2829 vaccinated and 607 placebo participants from four trials. Immunogenicity was assessed by measuring CHIKV serum neutralising antibody (SNA) titres (NT80) at selected time points; SNA NT80 ≥100 is the surrogate marker likely to predict protection. Immunogenicity and safety were assessed through Day 183 post vaccination.


Results

Immunogenicity findings showed robust responses, with a seroresponse (SNA NT80 ≥100) as early as Day 8(47%), peaking at Day 15 (96%) and Day 22 (97%; primary endpoint), and lasting through Day 183 (85%).In phase 3 trials, the seroresponse rate and geometric mean titre was significantly higher in the vaccine group than the placebo group at all time points. CHIKV VLP vaccine demonstrated a favourable safety profile across trials. Most AEs were mild or moderate; events primarily consisted of injection site pain, headache, fatigue, and myalgia. Solicited and unsolicited events of arthralgia were reported at similar rates between vaccinated and placebo participants. SAEs occurred in <1% of participants, with no vaccine-related deaths. Overall, no safety signals were detected.


Conclusions

CHIKV VLP vaccine offers a VLP-based vaccine option for immunisation against CHIKV disease. The data analysed demonstrate the strong immunogenicity and favourable safety profile of CHIKV VLP vaccine; rapid and durable SNA NT80 responses support the potential for this vaccine to protect individuals ≥12 years of age from disease caused by CHIKV.

Nipah virus (NiV) is an emerging bat-borne virus causing fatal encephalitis outbreaks in Bangladesh. Hence, we conducted this study to understand the epidemiology and evolutionary ecology of NiV spillover patterns in Bangladesh. Between 2001 and 2023, Bangladesh experienced 339 human cases of NiV infection across 221 spillover events in 32 districts, with a case fatality rate of approximately 70%. Notably, 40.72% of these events occurred in Faridpur and 27.15% in Naogaon, accounting for 150 spillovers from these two districts alone, indicating a higher prevalence of NiV in these regions. Both districts are known for their intense date palm sap (RDPS) production, a suspected source of NiV transmission, as 45.72% (155/339; 95% CI: 40.33–51.19) of cases were linked to RDPS consumption and bat exposure. Furthermore, 66.37% (225/339; 95% CI: 61.08–71.40) of cases were associated with cluster events, suggesting significant human-to-human transmission. We conducted environmental investigations to assess potential spillovers from bats to humans. We identified 117 Indian flying fox (Pteropus medius) bat roosts within 10 km radius of 51 outbreak epicenters across 19 districts. Environmental samples, including roost urine and bat swabs, were collected over three days per site. In 33.33% (17/51; 95% CI: 20.32–47.10) of spillover events, we identified nearby bat roosts, while 18.80% (22/117; 95% CI: 12.18–27.07) of the roosts tested positive for NiV, either through individual bat samples or roost urine. We further performed phylogenetic analysis of Nipah virus phosphoprotein of our 4 newly generated NiV sequences and publicly available sequences from Bangladesh and reference sequences from other countries. This revealed two distinct clades in Bangladesh (Clade 1 and Clade 2) that have intermingled geographically over time. Additionally, four amino acid sites under positive selection were identified, differentiating Malaysian and Bangladeshi strains, which cannot be explained by simple divergence over time, highlighting special evolutionary pressure. The analysis suggests a potential bat-to-human transmission pattern, with human NiV strains genetically closer to bat strains. This study highlights the role of bats in the transmission of NiV to humans in Bangladesh and underscores the importance of environmental monitoring, phylodynamics, molecular characterization, pathogenicity in understanding the virus's spread and evolution.