Asymptomatic and pre-symptomatic patients infected with COVID-19

Asymptomatic but infectious people have been reported in many infectious diseases. Examples include herpes, cytomegalovirus and respiratory diseases caused by viruses such as H1N1 or H5N1 influenza, being asymptomatic and pre-symptomatic people a reservoir hidden for detection systems.

The Chinese government first reported the infection as pneumonia of unknown origin in late December 2019; then in late January 2020, the WHO declared the outbreak a Public Emergency of International Concern, and on 11 March was elevated the alert level to pandemic. The epicentre of the disease was Wuhan City in Hubei Province in central China. Three characteristics were identified in the infection: an 83% attack rate declared as highly alarming, a wide spectrum of clinical manifestations in the patients (ranging from minor symptoms to pneumonia and death) along with evidence of the virus in a minority without any evidence of symptoms. The infection quickly spread in China and then cases began to be exported internationally.

There was increasing evidence supporting the contribution to the spread of infection by asymptomatic and pre-symptomatic patients with COVID-19. The speed with which the infection spreads suggests that transmission from unidentified (because asymptomatic) cases played a substantial role in the exponential increase in the number of infected patients.

A new study has searched empirical evidence about the presence of asymptomatic and pre-symptomatic carriers in the current COVID-19 pandemic and offers reflections on the implications in the context of the current measures taken to control it.

In this way, the evidence confirms COVID-19 transmission from people who were asymptomatic at the time, and a series of implications for health service response are laid out, since asymptomatic and pre-symptomatic carriers would be a hidden reservoir of COVID-19.

Link to the paper: https://doi.org/10.1101/2020.04.08.20054023

Editorial Disclaimer: information published during the 2020 COVID-19 pandemic may be updated frequently to reflect the dynamic nature of current understanding.

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