Publications by authors named "Na-Ra Yun"

Severe fever with thrombocytopenia syndrome (SFTS) is an acute febrile illness caused by the SFTS virus (SFTSV). We conducted this study to propose a scientific evidence-based treatment that can improve prognosis through changes in viral load and inflammatory cytokines according to the specific treatment of SFTS patients. This prospective and observational study was conducted at 14 tertiary referral hospitals, which are located in SFTS endemic areas in Korea, from 1 May 2018 to 31 October 2020.

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Hemorrhagic fever with renal syndrome (HFRS) is caused by hantaviruses. Data of 34 patients with HFRS hospitalized at Chosun University Hospital, South Korea, between 2010 and 2021 were retrospectively analyzed. Nested reverse transcription polymerase chain reaction (RT-nPCR) targeting the L segment of hantavirus and sequencing were used for diagnosis.

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Background: Thromboembolic events are a well-recognized cause of in-hospital deaths of patients with infectious diseases. However, thromboembolic events in patients with scrub typhus, caused by Orientia tsutsugamushi have rarely been reported. This study aimed to assess risk factors associated with thromboembolic events in patients with scrub typhus.

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The spread of COVID-19 has significantly increased research on antiviral drugs and measures such as case isolation and contact tracing. This study compared the effects of lopinavir/ritonavir and remdesivir on COVID-19 patients with a control group receiving no antiviral drugs. Patients confirmed to have a SARS-CoV-2 infection via real-time RT-PCR were divided into three groups: lopinavir/ritonavir, remdesivir, and control.

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We aimed to identify the risk factors for impaired cellular and humoral immunity after three doses of the SARS-CoV-2 vaccine. Six months after the third vaccine dose, T-cell immunity was evaluated using interferon-gamma release assays (IGRAs) in 60 healthy and 139 immunocompromised (IC) individuals, including patients with hematologic malignancy (HM), solid malignancy (SM), rheumatic disease (RD), and kidney transplantation (KT). Neutralizing antibody titers were measured using the plaque reduction neutralization test (PRNT) and surrogate virus neutralization test (sVNT).

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Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), the virus responsible for COVID-19, causes a spectrum of symptoms ranging from mild upper to severe lower respiratory tract infections. However, the dynamics of nucleocapsid (N) protein antigenemia and RNAemia are not fully understood. We conducted a cohort study involving 117 patients with clinically confirmed COVID-19, focusing on the kinetics of antigenemia and RNAemia and their association with various clinical characteristics.

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Background: Scrub typhus and severe fever with thrombocytopenia syndrome (SFTS) are the 2 most common tick-borne infectious diseases in Korea. Every year, an increasing number of cases are reported, which is a public health concern. Therefore, we aimed to investigate the prevalence of SFTS-scrub typhus coinfection in patients with SFTS.

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Introduction: We report the case of a 60-year-old male who was hospitalized with fever, headache, fatigue, nausea, and myalgia for six days.

Methodology: Polymerase chain reactions (PCR) were performed on patient blood samples, and four ticks were collected from the area the patient mowed. Indirect immunofluorescence assays (IFAs) were performed on serum samples to detect specific antibodies.

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Article Synopsis
  • COVID-19, caused by SARS-CoV-2, was studied to understand the antibody response in patients over a year after symptoms appeared, involving 314 serum samples from 97 patients.
  • The study used various tests to assess neutralizing antibodies, revealing that positivity rates were high shortly after infection but differed between asymptomatic and symptomatic patients over time.
  • While neutralizing antibodies appeared quicker in asymptomatic patients, they lasted longer in symptomatic and severe cases, highlighting differences in immune response based on the severity of the disease.
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Objective: The clinical implications of SARS-CoV-2 RNA viremia in blood (RNAemia) remain uncertain despite gaining more prognostic implications for coronavirus disease 2019 (COVID-19). However, the clinical relevance of SARS-CoV-2 RNAemia has not been well documented.

Methods: We conducted a cohort study on 95 confirmed COVID-19 patients and explored the prospects with evidence of SARS-CoV-2 RNAemia in association with various clinical characteristics.

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Coronavirus disease 2019 (COVID-19) is a novel infectious respiratory disease caused by SARS-CoV-2. We evaluated the efficacy of a plant-based human recombinant angiotensin-converting enzyme 2 (hrACE2) and hrACE2-foldon (hrACE2-Fd) protein against COVID-19. In addition, we analyzed the antiviral activity of hrACE2 and hrACE2-Fd against SARS-CoV-2 using real-time reverse-transcription PCR and plaque assays.

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This study analyzed HGA and SFTS in patients with suspected tick-borne infection by focusing on key differences that clinicians can easily recognize. A retrospective analysis was performed on confirmed patients with HGA or SFTS in 21 Korean hospitals from 2013 to 2020. A scoring system was developed by multivariate regression analysis and accuracy assessment of clinically easily discriminable parameters was performed.

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Article Synopsis
  • - Severe fever with thrombocytopenia syndrome (SFTS) is a tick-borne disease caused by the SFTS virus, with limited research on its prevalence among veterinary staff and their awareness levels.
  • - A study analyzed serum samples from 103 veterinary hospital employees, finding that a small number tested positive for SFTS, with a notable correlation between lower awareness of transmission risks and higher positivity rates.
  • - There is a significant gap in SFTS awareness among veterinary staff compared to veterinarians, highlighting the need for better training on safety precautions and personal protective equipment usage.
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  • - The research studied viral loads and diagnostic accuracy of upper and lower respiratory specimens for SARS-CoV-2 variants (wild-type, delta, and omicron) in 78 COVID-19 patients, finding omicron saliva samples had higher sensitivity than the other variants.
  • - Statistical analysis showed the omicron variant's sensitivity in saliva was significantly better compared to wild-type nasopharynx and sputum samples, while the viral loads among the different variants did not show significant differences.
  • - No significant difference in viral loads was found between vaccinated and nonvaccinated patients infected with the omicron variant, indicating that more research is needed to understand the causes of sensitivity variations in testing.
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Background: Severe fever with thrombocytopenia syndrome (SFTS) is an acute febrile disease caused by bites from ticks infected with the SFTS virus. In Korea, SFTS patients are observed nationwide, including Jeju Island, but there are currently no data regarding the national prevalence of SFTS, including that of residents of 16 cities and provinces. This study aimed to investigate the seroprevalence of SFTS in Korea.

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Article Synopsis
  • Whole-genome sequences of SARS-CoV-2 from 18 COVID-19 patients were analyzed to investigate genomic features and mutation patterns using next-generation sequencing techniques.
  • The study identified a total of 51 missense point mutations and deletions in key genomic regions, highlighting significant variations in protein-coding regions.
  • Phylogenetic analysis showed that clades V and GH are the most prevalent in the Gwangju region, with a correlation between high viral load and increased mutations, suggesting the need for further research on the virus's evolution and implications for treatment strategies.
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Background: Hemorrhagic fever with renal syndrome (HFRS) caused by hantaviruses is a frequently reported acute hemorrhagic fever in South Korea. These viruses are transmitted by various rodent species such as Apodemus agrarius.

Methodology/principal Findings: To investigate hantavirus infection and seroprevalence in rodents, wild rodents were captured from two districts in the suburbs of Gwangju Metropolitan City from January 2016 to December 2018.

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Severe fever with thrombocytopenia syndrome (SFTS) and scrub typhus are disorders with similar clinical features; therefore, differentiating between them is difficult. We retrospectively collected data from 183 SFTS and 178 scrub typhus patients and validated an existing scoring system to develop a more sensitive, specific, and objective scoring system. We first applied the scoring systems proposed by Kim et al.

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The clinical characteristics and the effect of viral RNA loads on fatality in 56 patients with severe fever with thrombocytopenia syndrome (SFTS) were analyzed. The non-survival group (12 patients) demonstrated a significantly higher mean age (77 years) than the survival group (44 patients, 65 years) (p = 0.003).

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Background: Severe fever with thrombocytopenia syndrome (SFTS) is an emerging tick-borne infectious disease caused by the SFTS virus (SFTSV). This syndrome is endemic in China, South Korea, and Japan, with a fatality rate of approximately 20-30%. Although the World Health Organization has listed SFTS as a disease that requires urgent steps for the development of its treatment, no treatments are available.

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The risk factors of environmental contamination by SARS-CoV-2 are largely unknown. We analyzed 1,320 environmental samples obtained from COVID-19 patients over 1 year. The risk factors for contamination of COVID-19 patients' surrounding environment were higher viral load in the respiratory tract and shorter duration from symptom onset to sample collection.

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Article Synopsis
  • - COVID-19, caused by the SARS-CoV-2 virus, has varying diagnostic accuracy for PCR tests recommended by the CDC and WHO, which is explored in a study involving 12 confirmed patients and 590 samples.
  • - The study found that a newly designed in-house RT-qPCR primer set (iNP) demonstrated significantly better sensitivity (94.8%) and specificity (100%) compared to WHO and CDC primers, especially in sputum samples.
  • - Results highlight the need for ongoing improvements in viral detection methods, emphasizing that sputum tests are the most effective, followed by nasopharyngeal and self-collected saliva samples.
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Rapid identification and effective isolation are crucial for curbing the spread of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). To meet this requirement, antigen-detection rapid diagnostic tests (Ag-RDTs) are essential. Between February 2020 and August 2020 we performed a cohort study of patients with confirmed COVID-19.

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Here, we aimed to investigate the diagnostic value of a serological assay using the nucleocapsid protein developed for severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) detection and evaluated its performance using three commercial enzyme-linked immunosorbent assays (ELISAs), namely, Standard E 2019 novel coronavirus disease (COVID-19) total antibody (Ab) ELISA (SD Biosensor), and EDI novel coronavirus COVID-19 IgG and IgM ELISA. A recombinant nucleocapsid protein (rNP) was expressed from plants and Escherichia coli for the detection of serum total Ab. We prospectively collected 141 serum samples from 32 patients with reverse transcription-PCR (RT-PCR)-confirmed COVID-19 and determined the sensitivity and dynamics of their total Ab response.

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Article Synopsis
  • The study investigated the relationship between viral loads and disease severity in COVID-19 patients by analyzing viral kinetics in 100 patients at Chosun University Hospital between February 2020 and May 2021.
  • Results showed that asymptomatic patients had lower viral loads compared to symptomatic and deceased patients, with the virus clearing faster in asymptomatic individuals.
  • Additionally, viral shedding persisted longer in severely affected patients, and steroid use was linked to lower cycle threshold values even among low-risk patients.
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