Montefiore Medical Center, Bronx, New York (E.A.M.).
Hospital of the University of Pennsylvania, Philadelphia, Pennsylvania (A.R.).
Ann Intern Med. 2021 Jan;174(1):69-79. doi: 10.7326/M20-5008. Epub 2020 Sep 17.
Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), the etiologic agent of coronavirus disease 2019 (COVID-19), has spread globally in a few short months. Substantial evidence now supports preliminary conclusions about transmission that can inform rational, evidence-based policies and reduce misinformation on this critical topic. This article presents a comprehensive review of the evidence on transmission of this virus. Although several experimental studies have cultured live virus from aerosols and surfaces hours after inoculation, the real-world studies that detect viral RNA in the environment report very low levels, and few have isolated viable virus. Strong evidence from case and cluster reports indicates that respiratory transmission is dominant, with proximity and ventilation being key determinants of transmission risk. In the few cases where direct contact or fomite transmission is presumed, respiratory transmission has not been completely excluded. Infectiousness peaks around a day before symptom onset and declines within a week of symptom onset, and no late linked transmissions (after a patient has had symptoms for about a week) have been documented. The virus has heterogeneous transmission dynamics: Most persons do not transmit virus, whereas some cause many secondary cases in transmission clusters called "superspreading events." Evidence-based policies and practices should incorporate the accumulating knowledge about transmission of SARS-CoV-2 to help educate the public and slow the spread of this virus.
严重急性呼吸综合征冠状病毒 2（SARS-CoV-2）是 2019 年冠状病毒病（COVID-19）的病原体，在短短几个月内就在全球范围内传播。现在有大量证据支持关于传播的初步结论，这些结论可以为合理的、基于证据的政策提供信息，并减少关于这一关键主题的错误信息。本文对该病毒传播的证据进行了全面综述。尽管有几项实验研究在接种后数小时从气溶胶和表面培养出活病毒，但在环境中检测到病毒 RNA 的实际研究报告的水平非常低，并且很少有分离出有活力的病毒。来自病例和聚集性报告的有力证据表明，呼吸道传播占主导地位，近距离接触和通风是传播风险的关键决定因素。在少数直接接触或经手传播被假定的情况下，尚未完全排除呼吸道传播。传染性在症状出现前一天左右达到高峰，并在症状出现后一周内下降，并且没有记录到患者出现症状约一周后的后续关联传播（late linked transmissions）。该病毒的传播动态存在异质性：大多数人不传播病毒，而有些病毒在称为“超级传播事件”的传播集群中导致许多继发性病例。基于证据的政策和实践应该纳入关于 SARS-CoV-2 传播的累积知识，以帮助教育公众并减缓该病毒的传播。
