RSV Epidemiology in Australia Before and During COVID-19

BACKGROUND AND OBJECTIVES: COVID-19 public health measures have altered respiratory syncytial virus (RSV) epidemiology, resulting in an unseasonal summer epidemic in Australia in 2020. We aimed to determine if the shifted RSV epidemic was more severe compared with previous years or if age-specific changes were associated with the resurgence. METHODS: Through this multicenter study, we analyzed routinely collected datasets from the Sydney Children's Hospitals Network in southeast Australia. We examined overall trends in RSV-related disease in children aged <16 years in 2020 compared with 2014-2019. We compared observed and expected counts for RSV infections, RSV-related hospitalizations, and emergency department visits for acute respiratory illness. RESULTS: In 2020, there was a shift in the peak of RSV-related disease from autumn and winter to early summer. Compared with previous years, the overall frequency of RSV infections increased in children aged 2 to 4 years (83.91%; 95% confidence interval [CI], 34.21% to 192.07%; P<.01). There was also an increase in the peak case counts of RSV infections and RSV-coded hospitalizations for some age groups. There was an overall reduction of RSV-coded hospitalizations (-31.80%; 95% CI, -41.13% to -18.96%; P<.01) and ICU admissions (-44.63%; 95% CI, -60.76% to -5.96%; P<.05) in 2020 compared with previous years. CONCLUSIONS: Our observations provide evidence that the shifted 2020 RSV season was no more severe than previous years. Increased RSV infections in children aged 2 to 4 years may be explained by a buildup in age-specific population susceptibility and increased testing in older children.