Effects of Non-Pharmacological Interventions on Respiratory Viruses Other Than SARS-CoV-2: Analysis of Laboratory Surveillance and Literature Review From 2018 to 2021.

Background: Since the global coronavirus disease 2019 (COVID-19) pandemic, non-pharmacological interventions (NPIs) such as extensive and comprehensive hand hygiene, mask-wearing, and social distancing have been implemented globally. This study aimed to investigate changes in respiratory viruses other than severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) that occurred following the implementation of these NPIs.

Methods: From January 2018 to December 2021, influenza-like illness patient specimens and specimens from the Korea Influenza and Respiratory Viruses Surveillance System were analyzed at the Incheon Metropolitan City Institute of Public Health and Environment. Oropharyngeal or nasopharyngeal swab samples from respiratory infection patients were transferred in a virus transport medium at 4°C. After RNA or DNA extraction, respiratory virus-specific genes for human influenza virus (IFV), adenovirus (ADV), parainfluenza virus (PIV), respiratory syncytial virus (RSV), human rhinovirus (hRV), human coronavirus, human bocavirus, and human metapneumovirus were detected by individual real-time reverse transcription polymerase chain reaction.

Results: A total 3,334 samples were collected. After NPI was implemented, the detection of respiratory viruses other than SARS-CoV-2 decreased overall. The yearly detection rate of respiratory viruses was decreased from 69.5% (399/574) in 2018 and 73.3% (505/689) in 2019 to 19.8% (206/1,043) in 2020 and 34.9% (365/1,028) in 2021. The epidemic was more prominent in respiratory viruses such as IFV and RSV, which were considered dominant viruses, especially those with viral envelopes. Among viruses that were not considered dominant, hRV showed no clear change before and after NPI, while PIV showed a rapid increase compared to the existing dominant viruses between October-December 2021, after the increase in the number of gatherings started at the end of September and the "Relaxing COVID19 and mitigation policy," which was implemented on November 1.

Conclusion: NPI seems to have influenced the isolation and transmission of respiratory viruses in South Korea. In the future, additional studies focusing on the isolation and transmission patterns of respiratory viruses following NPI are needed.