Infectious diseases are constantly evolving, and understanding their trends is crucial to keeping communities healthy. Our study examines how notifiable diseases in Australia changed over the last decade, including during the COVID-19 pandemic. This study, which analysed data from the National Notifiable Disease Surveillance System from 2012 to 2022, sheds light on patterns of various diseases and the impact of the pandemic's public health measures.

Our study found that prior to COVID-19, notifications for many infectious diseases were on the rise, especially respiratory and gastrointestinal infections. In contrast, diseases transmitted through blood or by vectors, such as viral hepatitis and vector-borne illnesses, showed a slight decline. We found an annual average increase of about 11% for all disease notifications from 2012 to 2019, with respiratory diseases leading this surge. These findings indicate shifts in healthcare engagement and public health policies, diagnostic technology, and possibly changing lifestyles.

With the onset of COVID-19 in 2020, Australia implemented some of the world's most stringent public health measures, including lockdowns, international travel restrictions, and social distancing mandates. The effects on other diseases were profound. Respiratory infections, such as the flu, dropped significantly due to reduced social interactions, masking, and sanitation protocols. However, by 2022, as restrictions eased, these infections rebounded significantly.

Interestingly, while COVID-19 measures decreased respiratory infections and imported diseases, we noted that some infections continued to rise, such as certain gastrointestinal diseases and STIs. This suggests that while some infections are closely tied to social behaviour and public movement, others are less influenced by these factors or might be indirectly affected by changes in healthcare access and behaviours during lockdowns.

Using pre-pandemic trends, we also estimated that over 200,000 cases of various infections were likely averted during the pandemic. We estimated that 65,000 fewer gastrointestinal infections and 121,000 fewer sexually transmitted infections were notified. These “averted cases” provide valuable insights, showing the influence of public health measures on infectious disease dynamics. While the declines in respiratory and imported infections were expected due to restricted travel and physical interactions, the reduction in other diseases highlights how closely healthcare access and behaviours are intertwined with transmission.

Why These Findings Matter

The study’s insights are significant for several reasons:

1. Public Health Preparedness: Knowing how diseases respond to interventions helps us prepare for future pandemics. Public health policies can be adapted to mitigate the risks of other infections when similar measures are necessary.

2. Healthcare Planning: These trends inform healthcare resource allocation and support the development of targeted vaccination, diagnostic, and treatment programs. 

This study provides a foundation for ongoing research. Future surveillance is essential to monitor whether these trends persist or shift again as communities adjust to a post-pandemic world. By understanding these trends, public health officials, researchers, and policymakers can make informed decisions that protect communities and create resilient health systems.