Department of Clinical Infectious Diseases, Toyama University Graduate School of Medicine and Pharmaceutical Sciences, Toyama, Japan.
Department of Microbiology, Toyama University Graduate School of Medicine and Pharmaceutical Sciences, Toyama, Japan.
PLoS One. 2020 Dec 9;15(12):e0243597. doi: 10.1371/journal.pone.0243597. eCollection 2020.
To investigate the relationship between viral load and secondary transmission in novel coronavirus disease 2019 (COVID-19).
Epidemiological and clinical data were obtained from immunocompetent laboratory-confirmed patients with COVID-19 who were admitted to and/or from whom viral loads were measured at Toyama University Hospital. Using a case-control approach, index patients who transmitted the disease to at least one other patient were analysed as "cases" (index patients) compared with patients who were not the cause of secondary transmission (non-index patients, analysed as "controls"). The viral load time courses were assessed between the index and non-index symptomatic patients using non-linear regression employing a standard one-phase decay model.
In total, 28 patients were included in the analysis. Median viral load at the initial sample collection was significantly higher in symptomatic than in asymptomatic patients and in adults than in children. Among symptomatic patients (n = 18), non-linear regression models showed that the estimated viral load at onset was higher in the index than in the non-index patients (median [95% confidence interval]: 6.6 [5.2-8.2] vs. 3.1 [1.5-4.8] log copies/μL, respectively). In adult (symptomatic and asymptomatic) patients (n = 21), median viral load at the initial sample collection was significantly higher in the index than in the non-index patients (p = 0.015, 3.3 vs. 1.8 log copies/μL, respectively).
High nasopharyngeal viral loads around onset may contribute to secondary transmission of COVID-19. Viral load may help provide a better understanding of why transmission is observed in some instances, but not in others, especially among household contacts.
研究 2019 年新型冠状病毒病（COVID-19）病毒载量与二次传播的关系。
从富山大学医院收治的免疫功能正常的实验室确诊 COVID-19 患者中获取流行病学和临床数据，对这些患者进行了病毒载量检测。采用病例对照方法，将至少将疾病传播给 1 名其他患者的指数患者分析为“病例”（指数患者），而未引起二次传播的患者（非指数患者，作为“对照”进行分析）。采用标准单相衰减模型的非线性回归，评估指数和非指数症状患者之间的病毒载量时间过程。
共纳入 28 例患者进行分析。在初始样本采集时，有症状患者的病毒载量中位数明显高于无症状患者，且成人高于儿童。在有症状患者（n = 18）中，非线性回归模型显示，指数患者的估计病毒载量起始值高于非指数患者（中位数[95%置信区间]：6.6[5.2-8.2]与 3.1[1.5-4.8]对数拷贝/μL，分别）。在成年（有症状和无症状）患者（n = 21）中，指数患者的初始样本采集时病毒载量中位数显著高于非指数患者（p = 0.015，分别为 3.3 与 1.8 对数拷贝/μL）。
发病时鼻咽部高病毒载量可能有助于 COVID-19 的二次传播。病毒载量可能有助于更好地理解为什么在某些情况下会发生传播，而在其他情况下则不会发生，尤其是在家庭接触者中。
