Background: We hypothesized that nationwide social distancing and other preventive measures for severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) were associated with reduced detection of other respiratory viruses in South Korea. Methods: We analyzed national surveillance data to compare incidence of respiratory viruses during 2016–2019 vs 2020. Results of multiplex reverse-transcription polymerase chain reaction assays for 8 respiratory viruses were included: adenovirus (ADV), parainfluenza virus (PIV), respiratory syncytial virus (RSV), influenza virus (IFV), human coronavirus (HCoV; non–SARS-CoV-2), human rhinovirus (HRV), human bocavirus (HBoV), and human metapneumovirus (HMPV). Results: During 2016–2019, rates of detection of respiratory viruses were relatively stable: ADV, 3.7%–9.2%; PIV, 1.4%–17.0%; RSV, 0.3%–15.3%; IFV, 0.4%–35.6%; HCoV, 1.5%–8.4%; HRV, 7.0%–25.1%; HBoV, 0.6%–6.3%; and HMPV, 0.7%–14.5%. Following implementation of social distancing in February 2020, rates of detection of enveloped viruses (HCoV, HMPV, IFV, PIV, and RSV) were significantly reduced by up to 100%. However, nonenveloped viruses (ADV, HRV, and HBoV) persisted throughout 2020, and HRV rates in hospitalized patients significantly increased. Conclusions: After implementation of social distancing for SARS-CoV-2 in South Korea, rates of detection of enveloped respiratory viruses decreased significantly, whereas nonenveloped viruses persisted, suggesting that enhanced infection prevention strategies are required to mitigate spread of these viruses.

Lee JJ, et al. J Korean Med Sci. 2021 Dec;36(50):e346. https://doi.org/10.3346/jkms.2021.36.e346

Objective Transmissibility of COVID-19 by children in the household is not clear. Herein, we describe children’s role in household transmission of COVID-19. Design and setting All paediatric COVID-19 index cases and their household members reported from 20 January to 6 April 2020 in South Korea were reviewed. The secondary attack rate (SAR) from child index case to household secondary case was calculated. Epidemiological and clinical findings of child index case-household secondary case pair was assessed. Results A total of 107 paediatric COVID-19 index cases and 248 of their household members were identified. One pair of paediatric index-secondary household case was identified, giving a household SAR of 0.5% (95% CI 0.0% to 2.6%). The index case was self-quarantined at home after international travel, stayed in her room, but shared a meal table with the secondary case. Conclusion The SAR from children to household members was low in the setting of social distancing, underscoring the importance of rigorous contact tracing and early isolation in limiting transmission within households.

Varicella (chickenpox) is an infectious disease caused by the highly contagious varicella zoster virus with a secondary attack rate greater than 90%. From this perspective, we aimed to establish the basis for a national varicella vaccine policy by reviewing vaccination programs and policies of countries that have introduced universal varicella vaccinations. As a result of the spread of varicella, an increasing number of countries are providing 2-dose vaccinations and universally expanding their use. In practice, the efficacy and effectiveness of vaccination differ among vaccines and vaccination programs. Optimized vaccination strategies based on each country’s local epidemiology and health resources are required. Accordingly, it is necessary to evaluate the effectiveness of varicella vaccines in different settings. Given the short-term and fragmented vaccine effectiveness evaluation in Korea, it is necessary to evaluate its effectiveness at the national level and determine its schedule based on the evidence generated through these studies.

In the context of the coronavirus disease 2019 pandemic, we aimed to systematically address the global seasonal patterns of human coronavirus (HCoV) infections. We identified relevant articles from MEDLINE, EMBASE, and CINAHL Plus as of May 11, 2020. The main outcomes were the peak months of HCoV infections each year and the months during which more than 5% of positive respiratory specimen tests were attributable to HCoV. Of 707 articles reviewed, 22 met the inclusion criteria. The annual percentage of HCoV infections reached a peak in February globally. We found a higher HCoV positivity rate among studies that tested only children (median: 5.9%, range: 0.9%–18.4%), compared with other studies of adults alone (median: 5.2%, range: 3.3%–7.1%) or the entire population (median: 1.9%, range: 0.2%–8.1%). We found the largest global peak of HCoV during the winter season, with the highest rate of positivity among children.

Kim DH, et al. J Korean Med Sci. 2020 Feb;35(12):e137. https://doi.org/10.3346/jkms.2020.35.e137