Prevalence of Asymptomatic SARS-CoV-2 Infection

Author(s): Oran DP and Topol DJ.

Annals of Internal Medicine 3rd June 2020

Respiratory infections
Epidemiology
General respiratory patient care
Public health

Digest Author(s): Stylianos Loukides, e-Learning Director / 6 June, 2020

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) has spread rapidly throughout the world since the first cases of coronavirus disease 2019 (COVID-19) were observed in December 2019 in Wuhan, China. Considering the data of COVID-19 infection approximately 40% of the people tested for COVID-19 infection are asymptomatic. The term asymtpomatic does not exclude transmission. In this review many items have been raised. First and most important, the absence of COVID-19 symptoms in persons infected with SARS-CoV-2 might not necessarily imply an absence of harm. For example, limited data exists regarding the association between asymptomatic individuals and lung findings in CT scans.

Another critical issue is the discrimination between the asymptomatic individuals from the merely presymptomatics ones. The asymptomatic individual is infected with SARS-CoV-2 but will never develop symptoms of COVID-19. In contrast, the presymptomatic individual is similarly infected but eventually will develop symptoms. So in order to analyze this specific phenotype we need longitudinal data.

In the current review the authors analyzed different cohorts from different parts of the world. The first observation was that a small fraction of asymptomatic persons may eventually develop symptoms. However, the observation period was extremely brief: a median of 2 days. 54% of the 76 asymptomatic persons on the Diamond Princess who were examined by computed tomography appeared to have significant subclinical abnormalities in their lungs. The absence of symptoms might not necessarily mean the absence of harm.

Finally, using data from the U.S.S. Theodore Roosevelt and considering the young age of the crew we may speculate that asymptomatic infection is more likely in younger persons.

Comments

Three major points:

  • The asymptomatic patient is mild for him/herself but not for the others.
  • We need longitudinal data in order to retrieve information for the pre-symptomatic ones.
  • In closed communities, we have to keep our efforts for surveillance and screening.