Altered epidemiological patterns of Respiratory Syncytial Virus and influenza detections in a tropical Australian setting 2020 to 2023.

BACKGROUND

We describe the recent temporal patterns of respiratory syncytial virus (RSV) and influenza virus detections in the Northern Territory (NT) of Australia, between 2020 and 2023.

METHODS

This retrospective analysis of patients presenting with respiratory diseases utilised a multiplex viral nucleic acid detection assay for RSV, influenza and SARS Cov2 (COVID-19) to determine the relative frequency of non-COVID-19 respiratory viral detections by age and month during the study period.

RESULTS

During this period of the NT COVID-19 epidemic, disruption of the usual annual wet season RSV outbreak patterns occurred, and the yearly influenza peak was absent for two annual cycles. Our data also reveals that 25% of RSV infections were occurring in patients greater than 40 years of age, compared to 32% of influenza infections presenting in the same period, documenting a greater burden of adult disease than previously documented in the NT.

CONCLUSIONS

Loss of non-COVID-19 viral seasonality and a substantial unrecognised RSV adult burden were noted. We will continue to monitor seasonality, and the RSV burden and this will help to target the populations benefiting from recently released RSV vaccine.