Physicists who study the behavior of galaxies posit the existence of invisible dark matter, which has mass but cannot be seen. The behavior of galaxies cannot be explained without the existence of something we cannot see (1). In this sense, asymptomatic infection is the dark matter of the current severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) pandemic. Asymptomatic infection is difficult to observe and characterize, by definition, as asymptomatic individuals are not sickened, do not present for care, and cannot be identified without testing. Nonetheless, the frequency with which such infection occurs is key to understanding the epidemiology of the pandemic. In PNAS, Sah et al. (2) provide a rigorous systematic review and metaanalysis of what we know about asymptomatic infection to date. Their review includes 390 studies—a testimonial to the intensity with which this question has been studied. Their results are important: Notwithstanding the virulence of SARS-CoV-2 infection, true asymptomatic infection is common (35%), and asymptomatic infection varies markedly by age, being far less common in older individuals (20%) than in children (47%), with symptomatic infection being more common in long-term care than other settings.

中文翻译：

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无症状感染者是大流行的暗物质【人口生物学】

研究星系行为的物理学家假设存在不可见的暗物质，它有质量但看不见。如果不存在我们看不到的东西，就无法解释星系的行为 ( 1 )。从这个意义上说，无症状感染者是当前严重急性呼吸系统综合症冠状病毒 2（SARS-CoV-2）大流行的暗物质。根据定义，无症状感染很难观察和表征，因为无症状感染者没有生病，也没有就医，未经检测就无法识别。尽管如此，这种感染发生的频率是了解大流行流行病学的关键。在 PNAS 中，Sah 等人。( 2) 对我们迄今为止对无症状感染的了解提供了严格的系统评价和荟萃分析。他们的审查包括 390 项研究——证明了这个问题的研究强度。他们的结果很重要：尽管 SARS-CoV-2 感染的毒力很强，但真正的无症状感染很常见（35%），无症状感染随年龄而异，老年人（20%）远不如儿童常见（47 %)，在长期护理中，症状感染比其他环境更常见。