Background and aim
Respiratory diphtheria is rare in Australia largely due to high vaccination coverage. On 20 December 2025, Western Australia (WA) confirmed its first case of toxigenic respiratory diphtheria in over 50 years, triggering a large-scale public health response across an Aboriginal community, two medical retrieval services and three hospitals in Kununurra, Broome and Perth.

Methods and analysis
A preliminary internal review of the response identified strengths and challenges. A multi-agency debrief was convened, informed by the review and a pre-debrief survey. Key themes included: geographic and timing challenges; access to diphtheria antitoxin; governance, coordination and communication; public health management; infection prevention and control (IPC); and specimen collection and testing. Findings were synthesised to identify system gaps and improvement opportunities.

Outcomes
Strong collaboration across health services supported a timely response despite remote-setting constraints and reduced workforce capacity preceding Christmas. Diphtheria antitoxin was sourced interstate and administered promptly, and booster vaccinations reached approximately 80% of the Aboriginal community. Challenges included inconsistent adherence to IPC precautions resulting in many healthcare worker contacts, and communication gaps including unclear result‑notification pathways. Without WA or national guidelines, teams relied on interstate guidance, with variation in interpretation when stratifying healthcare worker exposure risk. Subsequently, around 80 healthcare workers were classified as high-risk contacts requiring testing, antibiotics and furlough, with booster vaccination where indicated. Inconsistent transmission‑based precaution advice across key documents created uncertainty for IPC staff. Antimicrobial susceptibility and benzathine penicillin shortages complicated prophylaxis. Collectively, over 100 contacts required swabbing, placing pressure on laboratory capacity and necessitating urgent preparation of specialised media and prioritisation of testing.

Conclusion and future actions
A single case of diphtheria can create substantial operational burden, highlighting the need for clear, nationally consistent guidelines. Streamlined communication, strengthened local processes, and enhanced surge arrangements will support coordinated and resilient responses to future events.

Background and Aim
Residential Aged Care Facilities (RACFs) remain highly vulnerable to acute respiratory infections (ARI) such as influenza, respiratory syncytial virus (RSV), and COVID-19. The North Eastern Public Health Unit (NEPHU) provides support to 176 RACFs for ARI outbreak management. Despite similarities in transmission and available diagnostics for these ARIs, outbreak management policies differ between conditions; current policy requires asymptomatic testing during COVID-19 but not influenza or RSV outbreaks. The aim of this analysis was to compare respiratory outbreak characteristics in RACFs to inform outbreak management processes and identify opportunities to strengthen outbreak management systems.

Methods and Analysis
We analyzed outbreak data from June 2023–June 2025 from the NEPHU Outbreak Management System (OMS). RACFs report outbreaks via initial, interim, and final reports. Across 165 RACFs, 874 outbreaks were reported: 84.7% COVID-19 (9627 cases), 9.6% influenza (595 cases), and 5.7% RSV (429 cases). Mean outbreak duration was 16 days for COVID-19, 11 for influenza, and 18 for RSV. Attack rates were highest for COVID-19 (16.1%) compared to influenza (8.4%) and RSV (10.9%). Hospitalization rates were greatest for influenza (13.6%) compared to RSV (10.3%) and COVID-19 (2.5%). The case fatality rate was highest for RSV (4.7%) compared to influenza (3.5%) and COVID-19 (1.5%). No significant temporal trends were observed.

Outcomes
We observed greater proportionate morbidity and mortality in influenza and RSV outbreaks than COVID-19 outbreaks. This comparison is limited by the current policy to test asymptomatic residents during COVID-19 outbreaks, but not during influenza or RSV outbreaks. This may be impacting case ascertainment and the ability to directly compare rates of attack, morbidity and mortality.

Conclusion and Future actions
A broader, data-driven approach to communicable disease preparedness in aged care settings is essential. Outbreak analysis should guide consistent, severity-informed policies across respiratory pathogens.

Background and Aim
On 24 November 2025, an office-based public health unit with a hybrid working model and offices located in a hospital experienced multiple staff absences with influenza-like illness. This prompted an outbreak investigation to identify a source and advise on control and future prevention methods.

Methods and Analysis
We defined an outbreak case as working in the office and experiencing one or more symptoms of influenza between 17 and 30 November. We distributed a web-based survey and analysed for attack rates, onsets and office attendance. We also consulted with the hospital infection control team about concurrent ward outbreaks.

Outcomes
Of 46 survey responses (response rate 94%), 11 were cases (attack rate 24%) with influenza A detected on rapid testing in five. Onset was from 22 to 24 November, peaking on 22 November. All cases attended on 20 November and ten attended on 19 November (the one who didn’t attend tested positive, with onset 22 November).
Influenza A was present on nearby wards, with the first patient admitted on 20 November.
No cases occurred in people who work in individual rooms within the office. No social events explained transmission. No staff attended whilst unwell.

Conclusion and Future actions
This point-source influenza A outbreak had exposure on Thursday 20 November, evidenced by full case attendance on Thursday and peak onset on Saturday. Evidence suggested an external incursion of virus into the office, likely from the neighbouring ward, potentially through open doors onto the common corridor.
There is no outside ventilation in the office. Air purifiers were removed in 2024. Lack of ventilation could facilitate droplet and airborne transmission.
Staff worked offsite until the outbreak ended. No further transmission occurred. Recommendations included reinstallation of air purifiers in office spaces close to wards and consideration of relocating office-based teams far from patients.

Background:
Chickenpox (varicella) is a vaccine-preventable disease; however, recent increases in reported cases indicate growing susceptibility among healthcare workers and the broader community. Contributing factors include vaccine hesitancy, limited immunisation awareness, and uncertainty regarding individual vaccination histories. Within an emergency department (ED), failure to promptly identify and isolate suspected varicella cases can result in widespread exposure, necessitating extensive contact tracing by Infection Prevention and Control (IPC).
Methods:
A 29-year-old patient presented to the ED 4th November 2025, with a widespread vesicular rash following recent overseas travel. The initial diagnosis was impetigo, and a vesicle swab was taken. The patient remained in the ED waiting room for 6.5 hours without a mask. Varicella zoster virus (VZV) was confirmed 24 hours after the patient had left the ED. In response, all potentially exposed individuals received a notification advising that IPC would contact them regarding the exposure. Serology was added for patients with existing laboratory blood samples due to limited vaccine availability.
Results:
Eighty-six patients were in the ED waiting room during the exposure period. Of these, 76 (88%) were successfully contacted by IPC. Among the contacted patients, 48 (63%) underwent serological testing, resulting in 12 (16%) requiring vaccination; 28 (37%) required no follow-up based on prior varicella infection. There were 46 accompanying visitors; 42 (91%) were contacted. Among the contacted visitors six (14%) underwent serological testing; five (12%) required vaccination, while 31 required no further follow- up. In addition, 35 patients who transited through ED had serology added and all demonstrated VZV immunity. No secondary cases of VZV infection were detected.
Conclusion:
This incident highlights the critical need for improved early recognition, isolation practices, and communication strategies to effectively manage varicella exposures in the ED setting. Strengthening vaccination awareness and ensuring robust IPC processes will be essential to mitigating future risks.

Background and Aim
Inadequate ventilation in indoor settings allows exhaled respiratory particles to accumulate, increasing the risk of airborne transmission of respiratory infections. Schools are particularly high-risk environments, where large numbers of people share air for prolonged periods with typically poor ventilation. While ventilation and filtration technologies can reduce airborne pathogen exposure, evidence on their real-world implementation in community settings remains limited. The Pathway to Clean Indoor Air (PCIA) study, a multi-institutional collaboration led by the Burnet Institute with the Victorian Government. It evaluates the feasibility, acceptability, and effectiveness of indoor air quality (IAQ) interventions retrofitted in government schools and council buildings to reduce airborne transmission risk.

Methods and Analysis
This mixed-methods implementation study deployed heat recovery ventilation (HRV) and filtration systems across school classrooms and council facility rooms. Interventions targeted 14 L/s/person equivalent clean air delivery, the threshold proposed for minimising airborne transmission. Continuous CO₂ and PM₂.₅ monitoring was conducted during baseline and post-installation periods. Feasibility was evaluated through systematic documentation of installation challenges, and acceptability is assessed through structured surveys.

Outcomes
Baseline monitoring in schools (n=78 classrooms) demonstrated median ventilation rates of 2.1 L/s/person, well below the 14 L/s/person target. Median occupied-period CO₂ was 910 ppm, with several rooms substantially exceeding the 800 ppm threshold associated with elevated transmission risk. In-ceiling or wall-mounted installation was achieved in approximately 80% of rooms. Among rooms with HRV commissioned, median CO₂ reduced by 22% (1395 to 1082 ppm). Noise from wall-mounted units was the primary acceptability concern.

Conclusion and Future Actions

Retrofitted IAQ interventions are feasible and effective in standard building rooms, though building characteristics significantly influence installation approach. A toolkit of intervention options (in-ceiling, wall-mounted, and portable units) enables adaptation to diverse settings. Ongoing particle clearance testing, acceptability surveys, and economic evaluation will inform policy for scaling these interventions to reduce communicable disease transmission in community settings.

Background and Aim:

Pertussis (whooping cough) remains a significant public health concern in Australia and is a particular risk for infants too young to be vaccinated. Early diagnosis, prompt treatment, management of contacts and vaccination are essential to mitigate spread. However, due to high case volumes and prioritisation, only 18% of pertussis cases in the North Eastern Public Health Unit (NEPHU) catchment received direct public health advice via a phone interview in 2024-2025. To improve reach and timeliness of public health actions, NEPHU commenced sending a text message to all cases diagnosed with pertussis by PCR.

Methods and Analysis:

The text message was developed in consultation with general practitioners, consumers and legal representatives. From 25th August to 27th November 2025, all cases diagnosed with pertussis by PCR were sent a text message containing the diagnosis, public health advice for cases and contacts, and links to further information. An online evaluation survey was sent the following week to assess acceptability, utility, benefits, and risks of the text message.

Outcomes:

During the trial period, 165 cases were sent the text message, increasing the proportion of cases contacted by NEPHU from 18% to 91%. Of 38 evaluation survey respondents, 92% found the message helpful, 76% reported improved understanding of pertussis, and 76% undertook at least one public health action (i.e. isolation, notifying childcare/school, seeking treatment) as a result of receiving the text message. 97% of respondents expressed willingness to receive similar text messages for other notifiable conditions.

Conclusion and Future Actions

Text message is a feasible, acceptable, and effective method to deliver public health information about pertussis rapidly and at scale and can increase uptake of public health actions. Text messages and other digital communications offer an opportunity to enhance communicable disease control and responsiveness across a range of communicable diseases.

Background and Aim
Macrolides are widely used to treat Bordetella pertussis, yet macrolide-resistant B. pertussis (MRBP) strains are increasingly reported globally, with prevalence estimates ranging from 4.4% to 90%. MRBP infections are associated with more severe clinical disease and require alternative antibiotic therapy. Delayed detection can prolong inappropriate treatment and increases likelihood of ongoing transmission. Debate continues regarding which patients should undergo MRBP testing. This study compared infection burden, severity, mortality, epidemic peak timing, and inappropriate treatment across three diagnostic strategies: (1) testing all confirmed pertussis cases; (2) testing only severe cases; and (3) no MRBP testing.

Methods and Analysis
A Susceptible – Exposed – Infected – Recovered (SEIR) model was constructed to simulate pertussis transmission in Australia. Parameters included transmission probabilities, reproductive coefficient, age-specific severity and mortality, and demographic data from the Australian Bureau of Statistics. We modelled MRBP prevalence scenarios of 4.4%, 30%, 60%, and 90%, with five simulations per scenario, assessing trends and differences in outcomes across strategies over 12 months.

Outcomes
Incremental benefits of MRBP testing increased as prevalence rose, plateauing around 60%. Compared with Testing None, Testing All reduced infections by 10% (9-11%) at 4.4% prevalence, increasing to 47% (45-48%) at 60% and 90% prevalence. Testing Severe yielded smaller reductions: 3% (-1-5%) at 4.4% to 13% (12-13%) at 60%. Testing All delayed the epidemic peak by 5-6 weeks at ≥ 60% prevalence, whereas Testing Severe delayed it by 1 week. Across all scenarios, Testing All resulted in the lowest proportion of inappropriate treatment. No meaningful differences in severity or mortality were observed between strategies.

Conclusion and Future Actions
Routine MRBP testing for pertussis becomes important as MRBP prevalence rises in Asia-Pacific. Comprehensive testing may reduce transmission, delay outbreak peaks, and improve treatment appropriateness. Future work should evaluate implementation feasibility and economic impact to inform policy.