What is the range of illness severity of patients with coronavirus disease 2019 (COVID-19)?

Updated: Jun 16, 2020
  • Author: Medscape Drugs & Diseases; more...
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Patients with coronavirus disease 2019 (COVID-19) can be grouped into the following illness categories [2] :

  • Asymptomatic or presymptomatic infection: Individuals who test positive for severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) but have no symptoms

  • Mild illness: Individuals with any of various signs and symptoms (eg, fever, cough, sore throat, malaise, headache, muscle pain) without shortness of breath, dyspnea, or abnormal imaging

  • Moderate illness: Individuals with evidence of lower respiratory disease by clinical assessment or imaging and an oxygen saturation (SaO2) over 93% on room air at sea level

  • Severe illness: Individuals with a respiratory frequency of over 30 breaths per minute, SaO2 up to 93% on room air at sea level, ratio of arterial partial pressure of oxygen to fraction of inspired oxygen (PaO2/FiO2) below 300, or more than 50% lung infiltrates

  • Critical illness: Individuals with respiratory failure, septic shock, and/or multiple organ dysfunction.

In general, the prevalence of the range of illness severity is as follows [1] :

  • Mild to moderate (mild symptoms up to mild pneumonia): 81%

  • Severe (dyspnea, hypoxia, or >50% lung involvement on imaging): 14%

  • Critical (respiratory failure, shock, or multiorgan system dysfunction): 5%


In a Chinese study of over 44,000 patients, all deaths occurred among patients with critical illness, with a 2.3% overall case fatality rate but a 49% case fatality rate among patients with critical disease. [1]  In the Chinese pediatric population, there was a lower illness severity, with 94% having asymptomatic, mild or moderate disease; 5% having severe disease, and less than 1% having critical disease.

Among US COVID-19 cases with known disposition, 19% were hospitalized and 6% were admitted to the intensive care unit (ICU).

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