Department of Neurology, Boston Children's Hospital, Harvard Medical School, Boston, Massachusetts, USA.
Clin Infect Dis. 2020 Dec 17;71(10):2752-2756. doi: 10.1093/cid/ciaa654.
Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) spread rapidly in a few months despite global public health strategies to curb transmission by testing symptomatic patients and social distancing. This review summarizes evidence that highlights transmission by asymptomatic and presymptomatic individuals. Viral load of asymptomatic and symptomatic cases is comparable. Viral shedding is highest before symptom onset, suggesting high transmissibility before symptoms. Within universally tested subgroups, high percentages of SARS-CoV-2 infected asymptomatic individuals were found. Asymptomatic transmission was reported in several clusters, including a Wuhan study showing an alarming rate of intrahospital transmission. Several countries reported higher prevalence among healthcare workers than general population raising concern that healthcare workers could act as silent vectors. Therefore, current strategies that rely solely on "symptom onset" for infection identification need urgent reassessment. Extensive universal testing irrespective of symptoms may be considered, with priority placed on groups with high frequency exposure to positive patients.
严重急性呼吸综合征冠状病毒 2（SARS-CoV-2）在短短几个月内迅速传播，尽管采取了全球公共卫生策略，通过检测有症状的患者和保持社交距离来遏制其传播。本综述总结了强调无症状和有症状个体传播的证据。无症状和有症状病例的病毒载量相当。病毒脱落量在症状出现前最高，表明症状出现前具有高度传染性。在普遍检测的亚组中，发现了相当比例的 SARS-CoV-2 感染的无症状个体。在包括武汉研究在内的几个集群中都报告了无症状传播，武汉的研究显示出令人震惊的院内传播率。一些国家报告医护人员的感染率高于一般人群，这引发了人们对医护人员可能成为无声传播者的担忧。因此，目前仅依靠“症状出现”来识别感染的策略需要紧急重新评估。广泛的普遍检测无论症状如何都可能被考虑，优先考虑与阳性患者高频接触的群体。
