无症状传播是目前COVID-19控制策略的阿喀琉斯之踵

传统的感染控制和公共卫生策略主要依赖于疾病的早期发现，以控制其传播。当COVID-19突然出现在全球舞台时，公共卫生官员最初采用了用于在2003年控制严重急性呼吸道综合征（SARS）的干预措施，包括基于症状的病例检测和后续检测，以指导隔离和检疫。由于SARS-CoV-1和SARS-CoV-2有许多相似之处，包括高度的遗传相关性、主要通过呼吸道飞沫传播、常见下呼吸道症状（发热、咳嗽和气短）以及两种感染暴露后的潜伏期中位数均为5天，最初采用的这些方法是有理由的。然而，虽然采用了类似的控制干预措施，但这两种流行病的发展轨迹却存在巨大差异。SARS-CoV-1在有限地区感染约8,100人后，SARS在8个月内得到控制。然而，在5个月内，SARS-CoV-2已经感染了260多万人，并继续在世界各地迅速传播。

如何解释传播的这些差异？对于COVID-19的传染性，一个关键因素是SARS-CoV-2在上呼吸道的大量排毒¹，甚至在症状前患者中也有排毒，这是它与SARS-CoV-1的区别，SARS-CoV-1的复制主要发生在下呼吸道²。与症状相关的SARS-CoV-1病毒载量比SARS-CoV-2病毒载量晚5天（中位数）达到峰值，这使得基于症状的感染检测在SARS-CoV-1病例中更有效³。就流感而言，无症状感染者上呼吸道分泌物的病毒载量一般较下呼吸道分泌物的病毒载量低，而病毒排除的持续时间亦较有症状患者短⁴，这降低了症状少的患者传播疾病的风险。

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作者信息

Monica Gandhi, M.D., M.P.H., Deborah S. Yokoe, M.D., M.P.H., and Diane V. Havlir, M.D.
From the Department of Medicine, University of California, San Francisco.

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