Department of Infectious Disease Control, Daejeon Metropolitan Government, Daejeon, South Korea.
Department of Preventive Medicine, Konyang University College of Medicine, Daejeon, South Korea.
J Infect Dis. 2022 Mar 2;225(5):793-799. doi: 10.1093/infdis/jiab586.
The Delta variant of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) was the predominant variant worldwide at the time of this study. However, its transmission dynamics were unclear.
We analyzed 405 local cases infected with the Delta variant of SARS-CoV-2 and temporal patterns of viral shedding identified between 22 June and 31 July 2021 in Daejeon, South Korea.
Overall, 20% were presymptomatic at the time of epidemiological investigation. We identified 6 clustered outbreaks, and all were associated with indoor facilities. In 23 household contacts, the secondary attack rate was 63%. We estimated the mean serial interval as 3.26 days (95% credible interval, 2.92-3.60), and 15% (95% confidence interval, 13%-18%) of cases seeded 80% of all local transmission. Analysis of the nasopharyngeal swab samples identified virus shedding from the presymptomatic cases and the highest viral load was observed 2 days after symptom onset.
Our findings suggest that the Delta variant is highly transmissible in indoor settings and households. Rapid contact tracing, isolation of the asymptomatic contacts, strict adherence to public health measures, and increased uptake of coronavirus disease 2019 (COVID-19) vaccination, including booster doses, are needed to reduce community transmission of the Delta variant.
在本研究进行之时，严重急性呼吸综合征冠状病毒 2（SARS-CoV-2）的德尔塔变异株是全球主要的变异株。然而，其传播动态尚不清楚。
我们分析了 2021 年 6 月 22 日至 7 月 31 日在韩国大田市感染 SARS-CoV-2 的德尔塔变异株的 405 例本地病例，以及确定的病毒脱落的时间模式。
总体而言，在进行流行病学调查时，有 20%的患者处于无症状期。我们发现了 6 起聚集性暴发事件，所有事件均与室内设施有关。在 23 名家庭接触者中，二次攻击率为 63%。我们估计平均序列间隔为 3.26 天（95%可信区间为 2.92-3.60），15%（95%置信区间为 13%-18%）的病例引发了 80%的本地传播。对鼻咽拭子样本的分析表明，无症状病例存在病毒脱落现象，且在症状出现后 2 天观察到病毒载量最高。
我们的研究结果表明，德尔塔变异株在室内环境和家庭中具有高度传染性。需要迅速进行接触者追踪、对无症状接触者进行隔离、严格遵守公共卫生措施，并增加对 2019 冠状病毒病（COVID-19）疫苗的接种，包括加强针接种，以减少德尔塔变异株在社区中的传播。
