An analysis of health trends in 2025, informed by viral immunologist Professor Nathan Bartlett from the University of Newcastle and HMRI’s Infection Research Program, reveals a year marked by a variety of circulating pathogens and evolving disease patterns.
COVID-19 Presence
COVID-19 maintained a steady, low-level presence throughout 2025. It integrated into the broader mix of respiratory pathogens rather than causing major pandemic-era waves. NSW Health data indicated generally low virus levels, with moderate peaks observed in January and June. Several new variants emerged, including XEC and KW.1.1 early in the year, and XFG, NB.1.8.1, PE.1.4, and BA.3.2 increased toward the end of 2025.
Influenza and RSV Dynamics
Influenza showed an increased prevalence in 2025, particularly during the second half of the year. Professor Bartlett noted disruptions to typical respiratory pathogen patterns, including altered seasonality. Influenza and RSV co-circulated with SARS-CoV-2, at times outside their usual seasonal windows, leading to unpredictable peaks and multi-wave respiratory seasons. NSW Health data reflected a traditional winter flu wave peaking in July-August, alongside an additional surge in November and December. This early summer spike was attributed to a new variant of Influenza A (H3N2), subclade K. Respiratory syncytial virus (RSV) circulated at relatively low levels overall but disproportionately affected specific age groups. Nearly half of all lab-confirmed RSV cases in NSW were among children aged 0-4 years, with bronchiolitis-related hospital admissions in this demographic remaining stable compared to 2024.
Other Respiratory Infections
Additional respiratory pathogens continued to circulate in 2025, contributing to community illness and impacting health services:
- Human Metapneumovirus (hMPV): This pathogen experienced a global surge since late 2024, particularly in China and North America, leading to significant pediatric hospitalizations and posing risks for severe disease in immunocompromised individuals.
- Mycoplasma pneumoniae: After causing notable outbreaks in 2023 and 2024 in Asia and Europe, its prevalence declined in 2025. Infections often manifest as 'walking pneumonia' and have impacted outpatient care systems.
- Rhinovirus: Commonly known as the common cold, Rhinovirus constituted approximately two-thirds of all reported respiratory infections.
Non-Viral Outbreaks
Respiratory viruses were not the sole source of illness. A notable non-viral outbreak originated from alfalfa sprouts. A national recall of Parilla Fresh alfalfa sprouts was issued in November due to Salmonella contamination. An unusual strain of Salmonella affected over 44 individuals across Australia, including at least 18 in NSW. This incident highlighted the continued importance of food safety in public health.
Co-infections
2025 reflected a continued trend of co-infection, where individuals are infected with more than one pathogen concurrently. Mixed infections, encompassing both viral-viral and viral-bacterial combinations, became more common, particularly in children under five. Studies reported up to 34% of cases involving bacterial-viral co-infections, which complicates clinical management. Common examples included respiratory viruses like RSV or influenza alongside bacterial infections such as pneumonia or ear infections.
Vaccine-Preventable Diseases
Globally, 2025 saw an increase in vaccine-preventable diseases, a trend also observed in Australia. A resurgence in Whooping Cough (Pertussis) occurred post-pandemic, with some countries reporting tenfold increases compared to pre-pandemic baselines. Over 24,000 cases of Whooping Cough were recorded across Australia, with almost 9,400 in NSW. While the national total decreased from 57,000 in 2024, figures remained double those of 2019. Measles also resurged after years of low transmission in Australia, with over 160 national cases, including 30 in NSW, representing an increase from 57 confirmed cases in 2024.
Implications and Public Health Measures
Infectious disease patterns showed reduced predictability in 2025. With COVID-19 integrated into the broader respiratory pathogen mix, illness waves occurred at atypical times, increasing anticipation challenges. Professor Bartlett emphasized that disease surveillance is critical for rapid response and information dissemination, particularly for populations at high risk of severe disease, such as the very young, the elderly, immunocompromised individuals, and those with chronic illnesses. FluTracking, a joint initiative, provides a mechanism for public health contribution, where symptom reporting assists researchers and health authorities in early outbreak detection and response. Maintaining public health in 2025 involved vaccination, disease surveillance, and ongoing research in response to emerging threats.