How to classify disease severity for COVID-19



WhO logoCOVID-19 is the official name that was announced by the WHO sometime in February 2020 for the acute respiratory distress syndrome caused by some groups of the Coronavirus family. This disease became a global pandemic and its impact is still being felt worldwide till date.


The core symptoms of COVID-19 can present with varying degrees of severity and include:

  • fever, (~ 380C or 100.40F and above)
  • cough
  • shortness of breath and difficulty breathing. 


These core symptoms may appear as soon as two days or as long as 14 days after exposure. On average people show symptoms about five days after they are infected.


Atypical coronavirus symptoms have also been described. These include:

  • Fatigues
  • Chills
  • Shaking of body with chills
  • Body aches and headache
  • Sore throat
  • Digestive issues and lack of appetite
  • Sudden loss of smell and taste
  • Pink eyes
  • Skin rash
  • Heart issues
  • Stroke
  • Inflammed blotches on the skin of the toes ("Covid toes")
  • Neurological issues (including confusion, disorientation, loss of speech, memory impairment and lethargy)


This article will focus on how to clinically determine the severity of Covid-19 disease presentation.


According to the World Health Organization (WHO), the disease severity for COVID-19 can be clinically defined as:

  • Critical
  • Severe, and
  • Non-severe (mild/moderate)



Critical COVID-19 – Is defined clinically by the criteria for acute respiratory distress syndrome (ARDS), to include sepsis, septic shock, or other conditions that would normally require the provision of life-sustaining therapies such as mechanical ventilation (invasive or non-invasive) or vasopressor therapy.


Severe COVID-19 – Is defined clinically by any of the following criteria:

  • Signs of severe respiratory distress (in adults, accessory muscle use, inability to complete full sentences, respiratory rate > 30 breaths per minute; and, in children, very severe chest wall in-drawing, grunting, central cyanosis, or presence of any other general danger signs including inability to breastfeed or drink, lethargy, convulsions or reduced level of consciousness);
  • Oxygen saturation < 90% on room air;
  • Severe pneumonia.



Non-severe COVID-19 – Is defined clinically as the absence of any criteria for severe or critical COVID-19.


The infographics below diagrammatically depicts the different criteria for the clinical definition of Covid-19

Cartoon Showing Classification of Covid-19 dieases severity. Credit: WHO

Click image to enlarge. Credit: Co-produced by the BMJ and MAGIC; designer Will Stahl-Timmins (see BMJ Rapid Recommendations).



Click here for more detailed criteria for defining Covid-19 severity according to the WHO. (Acrobat reader is required to view data.)



Source: WHO: Clinical management of Covid-19: Living guidelines. Ver 6.0. Published Jan 12, 2023.



Published: January 21, 2023





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