Preprint Review Version 1 Preserved in Portico This version is not peer-reviewed

Asymptomatic COVID-19; We Don’t Know What We Don’t Know

Version 1 : Received: 23 July 2020 / Approved: 28 July 2020 / Online: 28 July 2020 (11:57:26 CEST)

How to cite: Brown, O.R. Asymptomatic COVID-19; We Don’t Know What We Don’t Know. Preprints 2020, 2020070681 (doi: 10.20944/preprints202007.0681.v1). Brown, O.R. Asymptomatic COVID-19; We Don’t Know What We Don’t Know. Preprints 2020, 2020070681 (doi: 10.20944/preprints202007.0681.v1).


Decisions affecting the COVID-19 pandemic, by the individual and those with highest authority, are being made on the basis of unreliable data. Data about cases and deaths are collected daily but represent only a sample of reality. Statistics convert sample data into more reliable estimates. However, statistics have no magical powers; reliability requires dependable data. It is futile to rail against this darkness; COVID-19 is not a scientific experiment. However, we must do better both with data collection and data analysis. In this review, I focus on one element of the data, the asymptomatic case of COVID-19. Without reliable information about this number, decision makers are significantly blinded. By its nature, the asymptomatic case is hidden but contaminating to understanding COVID-19. The true case rate and death rate per case are unknowable without knowing the fraction of cases that are asymptomatic. The best estimate of asymptomatic cases is in the CDC document: COVID-19 Pandemic Planning Scenarios. For four different scenarios the estimates range from 10% to 70%, with the best estimate of 40% for asymptomatic cases. However, even the definition of the asymptomatic case is problematic. In simplest terms, two elements are required: an infection and no symptoms. How is “no symptoms” to be usefully defined? It appears to be analogous to pontificating about black swans from studying only white swans. It implies infection, but how is infection defined? Is it presence of the virus, replication of the virus, or presence of antibodies? Is asymptomatic disease an oxymoron? Without extensive, purposeful screening for specifically defined, essential symptoms and appropriate virus and antibody testing over time, the class of asymptomatic cases remains unknown. Current estimates range from <20% to ˃80%. If low, it can be ignored; if high, it dramatically and proportionately lowers the case rate and the death rate per case. Consequentially, the asymptomatic rate dramatically affects our societal and political responses. In this focused review, we assess the limitations of the published estimates, bring attention to the importance of obtaining accurate data, and exhort that high priority be given in the scientific community to understanding the issue, asymptomatic COVID-19 cases.

Subject Areas

asymptomatic disease; communicability; COVID-19; death rate; Ro; SARS-CoV-2; social distancing; transmission rate; infection rate; quarantine

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