The Lancet Infectious Disease 2020.12.07

Although there have been more than 75,000 peer-reviewed and preprint publications on SARS-CoV-2 and COVID-19 since January, the size and characteristics of the persistently asymptomatic subpopulation remain poorly understood.

One of the main reasons for ongoing confusion about the proportion of asymptomatic infections is the lack of a consistent case definition.

Now, a team of international infectious disease experts has proposed a structured definition of ‘persistently asymptomatic SARS-CoV-2 infection’. They say the term should be reserved for people who have no known COVID-19 symptoms (including no atypical or mild symptoms) throughout the course of infection.

They recommend using the symptom list in the Canadian case definition at this time, which they say is the most comprehensive. A minimum follow-up period of 14 days from last possible exposure (or first positive test if exposure is unknown) is needed to differentiate pre-symptomatic from persistently asymptomatic individuals, they say.

The authors say the absence of a comprehensive understanding of asymptomatic SARS-CoV-2 infection makes it difficult to inform public health strategies on the best way to control the pandemic. Uncertainty about the existence, characteristics, prognosis, and role of asymptomatic SARS-CoV-2 infection in this pandemic will continue unless we have systematically and accurately collected data, they caution.