The severity of COVID-19 ranges from mild to critical diseases. However, limited data have been published on the detailed kinetics of viral load and host immune response throughout the disease course depending on disease severity. In this study, we comprehensively analyzed viral load, antibody responses to SARS-CoV-2, and cytokines/chemokines during the disease course, and identified the factors related to severity. Nasopharyngeal (NP) and plasma specimens were obtained from 31 patients with COVID-19 during hospitalization. Viral RNA in NP specimens was quantified by reverse transcription–PCR. Anti–SARS-CoV-2 antibodies and cytokines/chemokines in plasma specimens were analyzed by ELISA and cytometric bead array. The viral load in patients with COVID-19 peaked at the early stage of the disease and continuously decreased. Severe and critical cases showed higher viral load and prolonged viral shedding than asymptomatic and mild cases. Whereas plasma IgG was gradually increased and maintained during hospitalization, plasma IgM peaked at 3 weeks after symptom onset and dissipated. The antibody response in severe and critical cases was slightly delayed but stronger than those in others. High levels of interferon (IFN)-α, IFN-γ–induced protein-10, monokine induced by IFN-γ, and interleukin-6 at 5–10 days from symptom onset were associated with the severity of COVID-19. Our data indicate that high viral load in the respiratory tract and excessive production of cytokines and chemokines between 1 and 2 weeks from the symptom onset were significantly associated with the severity of COVID-19.

Skin and soft tissue infection (SSTI) is common and important infectious disease. This work represents an update to 2012 Korean guideline for SSTI. The present guideline was developed by the adaptation method. This clinical guideline provides recommendations for the diagnosis and management of SSTI, including impetigo/ecthyma, purulent skin and soft tissue infection, erysipelas and cellulitis, necrotizing fasciitis, pyomyositis, clostridial myonecrosis, and human/animal bite. This guideline targets community-acquired skin and soft tissue infection occurring among adult patients aged 16 years and older. Diabetic foot infection, surgery-related infection, and infections in immunocompromised patients were not included in this guideline.

Dexamethasone provides benefits in patients with coronavirus disease 2019 (COVID-19), although data regarding immunological profiles and viral clearance are limited. This study aimed to evaluate for differences in biomarkers among patients with severe COVID-19 who did and did not receive dexamethasone. We measured plasma biomarkers of lung epithelial/endothelial injury and inflammation in 31 patients with severe COVID-19 and in 13 controls. Changes in biomarkers and clinical parameters were compared during the 7-day period among COVID-19 patients, and also according to dexamethasone use. Thirty-two patients with severe COVID-19 who received mechanical ventilation (n = 6), high-flow nasal cannula (n = 11), and supplemental oxygen (n = 15) were analyzed. Relative to controls, patients with severe COVID-19 had significantly higher concentrations of biomarkers related to glycocalyx shedding (endocan and syndecan-1), endothelial injury (von Willebrand factor), and inflammation (soluble receptor for advanced glycation end-products [sRAGE] and interleukin-6). The 7-day decreases in biomarkers of endothelial injury (angiopoietin-2 [Ang-2] and intercellular adhesion molecule-1 [ICAM-1]) and sRAGE, but not in the biomarker of lung epithelial injury (surfactant protein D), were correlated with decreases in C-reactive protein and radiologic score at day 7. Twenty patients (63%) received dexamethasone, and the dexamethasone and non-dexamethasone groups differed in terms of disease severity. However, dexamethasone was associated marginally with increased SpO₂/FiO₂ and significantly with decreases in C-reactive protein and radiologic score after adjusting for baseline imbalances. Furthermore, the dexamethasone group exhibited a significant decrease in the concentrations of Ang-2, ICAM-1, soluble form of the Tie2 receptor (a biomarker of glycocalyx shedding), and sRAGE. Both groups exhibited a clinically insignificant increase in the cycle threshold value. Severe COVID-19 may be characterized by more severe endothelial injury and inflammation, and less severe lung epithelial injury. There is a possibility that dexamethasone improved severe COVID-19 and related endothelial injury without delaying viral clearance.

It remains unclear whether high titers of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) antibodies aggravate clinical manifestations in patients or whether severe clinical manifestations result in high antibody titers. Thus, we investigated the cause–effect relationship between SARS-CoV-2 antibody titers and disease severity. We prospectively enrolled patients admitted with the diagnosis of coronavirus disease-19 (COVID-19) from February 2020 to August 2020. We measured SARS-CoV-2 antibody titers, namely anti-receptor-binding domain (RBD) antibody and neutralizing antibody (NAb), from blood samples and calculated the chest radiograph (CXR) scores of the patients to evaluate the severity of COVID-19. Overall, 40 patients with COVID-19 were enrolled. Pneumonia was observed in more than half of the patients (25/40, 60%). SARS-CoV-2 antibody titers were higher in patients who were aged >60 years (anti-RBD antibodies, P = 0.003 and NAb, P = 0.009), presented with pneumonia (P = 0.006 and 0.007, respectively), and required oxygen therapy (P = 0.003 and 0.004, respectively) than in those who were not. CXR scores peaked (at 15–21 days after the onset of symptoms) statistically significantly earlier than SARS-CoV-2 antibody titers (at 22–30 days for NAb and at 31–70 days for anti-RBD antibody). There was a close correlation between the maximum CXR score and the maximum SAR-CoV-2 antibody titer. Based on the comparison of the peak time of SARS-CoV-2 antibody titers with the CXR score after symptom onset, we suggest that severe clinical manifestations result in high titers of SARS-CoV-2 antibodies.

During the coronavirus disease (COVID-19) pandemic, social distancing was effective in controlling disease spread across South Korea. The impact of national social distancing on the spread of common respiratory virus infections has rarely been investigated. We evaluated the weekly proportion of negative respiratory virus polymerase chain reaction (PCR) test results and weekly positive rates of each respiratory virus during the social distancing period (10th–41st weeks of 2020) and the corresponding period in different years, utilizing the national respiratory virus surveillance dataset reported by the Korean Center for Disease Control and Prevention. The proportions of negative respiratory virus PCR test results increased up to 87.8% and 86.1% during level 3 and level 2 of the social distancing period, respectively. The higher the level of social distancing, the higher the proportion of negative respiratory virus PCR test results. During the social distancing period, the mean weekly positive rates for parainfluenza virus, influenza virus, human coronavirus, and human metapneumovirus were significantly lower than those during the same period in 2015–2019 (0.1% vs. 9.3%, P <0.001; 0.1% vs. 7.2%, P <0.001; 0.4% vs. 2.3%, P <0.001; and 0.2% vs. 5.3%, P <0.001, respectively). The mean positive rate for rhinovirus/enterovirus during level 3 social distancing was lower than that in the same period in 2015–2019 (8.5% vs. 19.0%, P <0.001), but the rate during level 1 social distancing was higher than that in the same period in 2015–2019 (38.3% vs. 19.4%, P <0.001). The national application of social distancing reduced the spread of common respiratory virus infections during the COVID-19 pandemic.

Early in vitro studies have suggested that hydroxychloroquine (HCQ) is a potentially useful drug against severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infections. This study was conducted to determine whether HCQ had a preventive effect on coronavirus disease 2019 (COVID-19) in rheumatic disease patients who were taking HCQ. We conducted a population-based retrospective cohort study using the records of the Korean Health Insurance Review and Assessment (HIRA) claim records. The clinical data of patients with rheumatoid arthritis (RA) or systemic lupus erythematosus (SLE) who were tested for SARS-CoV-2 were investigated. We compared the attack rate of COVID-19 between those who underwent HCQ therapy within 14 days before the test for SARS-CoV-2 (HCQ users) and HCQ non-users. Data were analysed using logistic regression models, χ2, and Student's t-tests. As of 15th May 2020, 2066 patients with RA or SLE were tested for COVID-19. Among them, 31.4% (649/2066) were treated with HCQ. Most HCQ users (93.7%, 608/649) were taking 200-400 mg/day recommended for the treatment of rheumatic diseases. The attack rate of COVID-19 in the HCQ users (2.3%, 15/649) did not differ from that in the HCQ non-users (2.2%, 31/1417) (p 0.86). HCQ prophylactic use at a usual dose did not prevent COVID-19 in patients with rheumatic disease.