COVID-19 symptoms resources

The SMC collated resources related to COVID-19 symptoms.


SMC alerts

13 Aug 2020: Spotting COVID-19 symptoms – Expert Reaction

7 May 2020: Factors that make people more vulnerable to COVID-19 – Expert Q&A 

30 April 2020: Unusual COVID-19 symptoms – Expert Reaction 

18 March 2020: Treatment of COVID-19 patients – Expert Q+A



SARS-CoV-2 infection can cause a range of symptoms. Unlike a cold or flu Covid-19 is considered a multi-organ disease, affecting more than just the respiratory system. Knowledge about symptoms and conditions is still developing. 

There are a broad range of symptoms, some are more common than others. Symptoms can develop slowly. A general overview of symptoms is provided by the New York Times. The average incubation period (the time from exposure to symptom onset) for Covid-19 is about 5 days (with a range of 2-7 days).

The most common symptoms, based on current evidence, are:

  • Fever (70%-90% of cases)
  • Dry cough (60%-86%)
  • Changes in sense of smell and/or taste (64% to 80%)
  • Shortness of breath (53%-80%)
  • Fatigue (38%)
  • Muscle pains (15%-44%)
  • Nausea or diarrhea (15%-39%)
  • General weakness (25%)

 Less common symptoms include:

  • Dizziness 
  • “Brain fog”
  • Eye discomfort
  • Rashes
  • Blisters on fingers or toes
  • Blood clots

One study (not yet peer reviewed) involving patients in the UK, the US and Sweden identified six clusters of symptoms that were generally present five days after symptom onset:

  • Cluster 1: Upper respiratory tract symptoms (eg, persistent cough, and muscle pain). Very few (1.5%) patients needed respiratory support, and 16% of them made at least a trip to the hospital.
  • Cluster 2: Upper respiratory tract symptoms, with a higher frequency of skipped meals, and fever. In this group 4.4% needed respiratory support, and 17.5% made one or more visits to the hospital.
  • Cluster 3: Gastrointestinal symptoms like diarrhea, but few other symptoms. 3.7% of patients in this group needed respiratory support, and 24% made at least one visit to the hospital.
  • Cluster 4: Early signs of severe fatigue, continuous chest pain, and cough. 8.6% of patients needed respiratory support, and 23.6% went to the hospital at least once.
  • Cluster 5: Confusion, skipped meals, severe fatigue. 9.9% of patients needed respiratory support, and 24.6% went to the hospital at least once.
  • Cluster 6: Marked respiratory distress, the onset of breathlessness, chest pain, confusion, fatigue, gastrointestinal symptoms. As many as 20% of the patients in this group needed respiratory support, and 45.5% went at least once to the hospital.

Clusters 1 and 2 were assessed as being relatively mild, while those in clusters 5 & 6 at day five after symptoms appeared had significant risk of later being hospitalised and requiring respiratory support.

Medical complications

The most common medical complications associated with Covid-19 are: 

  • Pneumonia (75% of cases with complications)
  • Acute respiratory distress syndrome (15%)
  • Acute liver injury (19%) 
  • Cardiac injury (7%-17%)
  • Acute heart failure or other cardiac problems (10%-25%)
  • Acute kidney injury (9%)
  • Neurological impairments (8%)
  • Acute cerebrovascular disease (3%)
  • Shock (6%) 
  • Multisystem inflammatory syndrome (very rare, but affecting some children)

Some of these conditions may be due more to an overstimulated immune response rather than being directly caused by the virus. There is uncertainty about whether the infection causes (infrequently) some other conditions, such as diabetes.

About 5% of patients with severe symptoms can require intensive care, and more than 75% of hospitalised patients have needed oxygen.

Studies are identifying that a strong indicator for development of severe complications to the infection is an excessive inflammatory response by the patient’s immune system.


Approximately 25% of infected patients have comorbidities, but 60% to 90% of those hospitalized have comorbidities. The most common comorbidities in hospitalized patients include:

  • Hypertension (present in 48%-57% of patients)
  • Diabetes (17%-34%)
  • Cardiovascular disease (21%-28%)
  • Chronic pulmonary disease (4%-10%)
  • Chronic kidney disease (3%-13%)
  • Malignancy (6%-8%)
  • Chronic liver disease (<5%)
  • Obesity and overweight can also be important risk factors, especially for risk of death

Asymptomatic cases

The proportion of infected people who don’t develop symptoms is uncertain. Estimates vary widely, based on particular circumstances, and how long people are monitored. In some cases it can be very high (more than 80%), while in other cases it can be less than 10%. Assessments are trending toward an overall proportion of 30% to 40% of infections being asymptomatic (or at least people not recognising symptoms).

Even if people do not develop symptoms, they can still develop tissue damage, such as lung abnormalities