The epidemiology of notifiable diseases in Australia and the impact of the COVID-19 pandemic, 2012-2022

Background: Infectious disease surveillance tracks disease epidemiology and informs prevention and control. Public health measures implemented in Australia during the COVID-19 pandemic (2020 to 2022) affected infectious disease epidemiology. We examined notifiable disease epidemiology in Australia from 2012 to 2022, evaluating disease trends and pandemic impacts.

Methods: We analysed case notifications supplied to the Australian National Notifiable Disease Surveillance System (NNDSS) from 1 January 2012 to 31 December 2022. The annual incidence and notification incidence trends were calculated and the average changes in annual incidence were investigated by Poisson regression.

Results: Over the study period, there were 14,087,045 notifications of 68 diseases. Respiratory diseases were the most commonly notified disease group (83% of all notifications) and vector-borne diseases the least (< 1%). The ten highest-incidence diseases comprised 97% of all notifications over the study period, with COVID-19 alone accounting for 72%. Notifications were most common among the 20-39-year age group (37%). From 2012-2019, notification incidence of gastrointestinal, respiratory and sexually transmissible infections increased, whereas for bloodborne viral hepatitis, vector-borne diseases and imported diseases it decreased. From 2020-2021, average notification incidence of most non-COVID-19 respiratory diseases decreased compared to the 2012-2019 period; sexually transmissible infections notification incidence remained fairly stable; notification incidence of some gastrointestinal diseases increased while others decreased; and notification of imported diseases markedly decreased. A rebound in notification incidence was seen for most diseases in 2022.

Conclusions: Prior to the COVID-19 pandemic, most notifiable diseases had increasing notification incidence, except for bloodborne viral hepatitis, vector-borne diseases and imported diseases. COVID-19-related public health measures had variable impacts on notifiable diseases.