Feeling under the weather in 2025? You weren't alone! From the familiar sniffles to unexpected outbreaks, 2025 threw a lot at us in terms of illnesses. Let's dive into what made so many people sick, according to Professor Nathan Bartlett, a viral immunologist from the University of Newcastle and HMRI's Infection Research Program. This information provides valuable insights into the pathogens and health trends that shaped the year.
COVID-19: A Persistent Presence
COVID-19, while not causing the massive waves seen during the pandemic, maintained a steady, low-level presence throughout 2025. Professor Bartlett explained that it has become part of the broader mix of respiratory pathogens circulating in the community. NSW Health data suggests that virus levels generally remained low, with moderate peaks in January and June. Several new variants emerged, including XEC and KW.1.1 early in the year, with XFG, NB.1.8.1, PE.1.4, and BA.3.2 increasing toward the end of 2025.
Influenza and RSV: Unpredictable Seasons
Influenza made a noticeable comeback in 2025, especially in the second half of the year. Professor Bartlett noted significant disruption to the usual patterns of respiratory pathogens since the COVID years, including disrupted seasonality. Influenza and RSV are now co-circulating with SARS-CoV-2, sometimes outside their usual seasonal windows, leading to unpredictable peaks and 'multi-wave' respiratory seasons. While NSW Health data reflected a traditional winter flu wave, with a July-August peak, an unexpected surge occurred in November and December. This early summer spike was driven by a new variant of Influenza A (H3N2), called subclade K.
Respiratory syncytial virus (RSV) circulated at relatively low levels overall in 2025, but its impact was not evenly felt across all age groups. Nearly half of all lab-confirmed cases of RSV in NSW were in children aged 0-4 years, according to NSW Health, with bronchiolitis (commonly caused by RSV) hospital admissions in this age group remaining stable compared to 2024.
Other Respiratory Infections: Beyond the Usual Suspects
Several other respiratory pathogens continued to circulate in 2025, contributing to community illness and putting pressure on health services. Globally, respiratory pathogens like Human Metapneumovirus (hMPV) have re-emerged. Professor Bartlett noted that since late 2024, hMPV has surged globally, notably in China and North America, causing significant paediatric hospitalizations and raising concerns about severe disease in immunocompromised individuals. He also pointed to Mycoplasma pneumoniae, which caused large outbreaks in 2023 and 2024 in Asia and Europe before declining in 2025. These infections often present as 'walking pneumonia' and have stressed outpatient care systems. And while Rhinovirus often flies under the radar, the common cold remains one of the biggest contributors to illness, accounting for around two-thirds of all respiratory infections seen in the community.
Non-Viral Outbreaks: When Food Becomes the Foe
Respiratory viruses weren't the only culprits making us sick in 2025. One of the largest non-viral outbreaks came from an unexpected source: alfalfa sprouts. A national recall of Parilla Fresh alfalfa sprouts was issued in November due to Salmonella contamination. The unusual strain of Salmonella affected more than 44 people across Australia, including at least 18 in NSW. This incident served as a stark reminder that food safety remains a crucial part of public health.
Co-infections: A Growing Trend
2025 saw a continuation of the rising trend of co-infection, where people are infected with more than one pathogen at the same time. Professor Bartlett said that mixed infections, both viral-viral and viral-bacterial, have become more common, especially in children under five. Studies report up to 34% of cases involving bacterial-viral co-infections, complicating clinical management. Common examples of co-infections include a respiratory virus like RSV or influenza alongside a bacterial infection such as pneumonia or an ear infection.
Preventable Diseases: A Concerning Resurgence
Here's where it gets concerning: 2025 brought an increase in illnesses that can be prevented by vaccination around the world, and Australia was not immune to this trend. Professor Bartlett stated that globally, there has been a dramatic resurgence in vaccine-preventable diseases like Whooping Cough post-pandemic, with some countries reporting 10-fold increases compared to pre-pandemic baselines. There were more than 24,000 cases of Whooping Cough (Pertussis) recorded across Australia this year, with almost 9400 in NSW. While the national total dropped from 57,000 in 2024, the figures were still double what they were in 2019. There was also a resurgence in measles after years of very low transmission in Australia, with more than 160 cases recorded nationally, including 30 in NSW. That’s an alarming increase from just 57 confirmed cases in 2024.
So, what can we learn from 2025?
The last 12 months highlighted that infectious diseases are no longer following predictable patterns. With COVID-19 now part of the broader mix of respiratory pathogens, waves of illness can emerge at unexpected times, making them harder to anticipate. Professor Bartlett explained that this means disease surveillance is more important than ever, allowing for faster reaction time and information dissemination to help protect us all, particularly those most at risk of severe disease, including the very young, the elderly, the immunocompromised, and people with chronic illnesses. FluTracking, a joint initiative of the University of Newcastle, Hunter New England Health, and HMRI, is one way people can contribute to public health. By reporting symptoms in just 30 seconds each week, the community can help researchers and health authorities detect outbreaks earlier and respond faster. 2025 showed that staying healthy relies on vaccination, disease surveillance, and ongoing research working together to protect the community when new threats emerge.
What are your thoughts? Did any of these trends surprise you? Are you concerned about the rise in vaccine-preventable diseases? Share your opinions in the comments below! Let's start a conversation about how we can stay healthy in an ever-changing world.
