Nationwide Social Distancing and the Epidemiology of Severe Acute Respiratory Infections

Nonpharmaceutical interventions (e.g., social distancing) are recommended to prevent the spread of respiratory viruses. However, few epidemiological studies have assessed whether social distancing in actual settings reduces the disease burden of severe acute respiratory infections (SARIs) in the general population. Accordingly, we aimed to assess associations between nationwide social distancing for coronavirus disease 2019 (COVID-19) and non-COVID-19 SARIs. We collected data on SARI epidemiologic characteristics recorded from January 2018 through December 2020 from the nationwide sentinel SARI surveillance data maintained by the Korea Disease Control and Prevention Agency. The number of SARIs per 1000 hospitalized patients decreased significantly to 18.61, 18.15, and 6.25 in 2018, 2019, and 2020 (p<0.001), respectively, during the surveillance period of 3 years. The number of intensive care unit admissions associated with SARIs per 1000 hospitalized patients was 0.83, 0.69, and 0.54 in 2018, 2019, and 2020 (p< 0.001), respectively, and the number of SARI-associated mortalities per 1000 patients was 0.42, 0.29, and 0.27 in 2018, 2019, and 2020 (p<0.001), respectively. Moreover, SARIs had two peak seasons in 2 years of the surveillance period (2018 and 2019). However, seasonality was not observed since social distancing was initiated. Our sentinel surveillance data demonstrated a remarkable reduction in SARI disease burden and a change in seasonality following the implementation of nationwide social distancing. Accordingly, we suggest that social distancing could be effective in forthcoming seasonal epidemics of non-COVID-19 origin, although the impact thereof on other aspects of society needs to be carefully considered.