J Korean Med Sci.  2024 May;39(19):e171. 10.3346/jkms.2024.39.e171.

Epidemiology of Respiratory Viruses in Korean Children Before and After the COVID-19 Pandemic: A Prospective Study From National Surveillance System

• Cho HJ
• Rhee JE
• Kang D
• Choi EH
• Lee NJ
• Woo S
• Lee J
• Lee SW
• Kim EJ
• Yun KW

• KMID: 2555915
• DOI: http://doi.org/10.3346/jkms.2024.39.e171

Abstract

Background
The coronavirus disease 2019 (COVID-19) pandemic led to a decrease in the seasonal incidence of many respiratory viruses worldwide due to the impact of nonpharmaceutical interventions (NPIs). However, as NPI measures were relaxed, respiratory viral infections re-emerged. We aimed to characterize the epidemiology of respiratory viruses in Korean children during post-COVID-19 pandemic years compared to that before the pandemic.
Methods
A nationwide prospective ongoing surveillance study has been conducted for detection of respiratory viruses between January 2017 and June 2023. We included data on adenovirus (AdV), human bocavirus (HBoV), human coronavirus (HCoV), human metapneumovirus (HMPV), human rhinovirus (HRV), influenza virus (IFV), parainfluenza virus (PIV), and respiratory syncytial virus (RSV), which were detected in children and adolescents younger than 20 years. We analyzed the weekly detection frequency of individual viruses and the age distribution of the affected children. The study period was divided into prepandemic (2017–2019) and postpandemic (2021–2023) periods.
Results
A total of 19,589 and 14,068 samples were collected in the pre- and postpandemic periods, respectively. The overall detection rate of any virus throughout the study period was 63.1%, with the lowest occurring in the 2nd half of 2020 (50.6%) and the highest occurring in the 2nd half of 2021 (72.3%). Enveloped viruses (HCoV, HMPV, IFV, PIV, and RSV) almost disappeared, but nonenveloped viruses (AdV, HBoV, and HRV) were detected even during the peak of the COVID-19 pandemic. The codetection rate increased from 15.0% prepandemic to 19.1% postpandemic (P < 0.001). During the postpandemic period, a large out-of-season PIV and HMPV epidemic occurred, but the usual seasonality began to be restored in 2023. The mean age of children with each virus detected in 2023 was significantly greater than that in prepandemic years (P = 0.003 and 0.007 for AdV and HCoV, respectively; P < 0.001 for others). The mean age of children with IFV increased in 2022 (11.1 ± 5.2 years) from prepandemic years (7.9 ± 4.6 years) but decreased to 8.7 ± 4.1 years in 2023.
Conclusion
With the relaxation of NPI measures, several seasonal respiratory viruses cocirculated with unusual seasonal epidemic patterns and were associated with increasing age of infected children.

Keyword

Respiratory Viruses; Epidemic; Children; COVID-19 Pandemic; Korea

Figure

• 

  Fig. 1 Seasonal variation in the detection of respiratory viruses in Korean children, January 2017–June 2023.HRV = human rhinovirus, HBoV = human bocavirus, AdV = adenovirus, HCoV = human coronavirus, RSV = respiratory syncytial virus, IFV = influenza virus, PIV = parainfluenza virus, HMPV = human metapneumovirus.

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  Fig. 2 Half-annual rate of viral codetection among Korean children, January 2017–June 2023.NPI = nonpharmaceutical intervention, COVID-19 = coronavirus disease 2019.

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  Fig. 3 Mean age of Korean children with each virus detected, January 2017–June 2023.HRV = human rhinovirus, HBoV = human bocavirus, AdV = adenovirus, PIV = parainfluenza virus, RSV = respiratory syncytial virus, HMPV = human metapneumovirus, HCoV = human coronavirus, IFV = influenza virus.The blue dot represents the mean age within 2 standard deviations. Above the values, the *** represents results with P < 0.001 and * represents those with P < 0.05.

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