Clinical characteristics of COVID-19

7th Jan 2021

Healthcare workers and researchers are working tirelessly to understand the clinical characteristics of COVID-19. 

Here, we’ll review what we know about the clinical characteristics of SARS-CoV-2 from several large-scale studies. These articles provide insight on the severity, age distribution, risk factors, and mortality rate of COVID-19. 

 

Classifying the severity of COVID-19

The best estimates today come from a study of over 72 000 COVID-19 cases in Wuhan, China. This study showed that 81% of people with COVID-19 have mild disease, 14% have severe disease, and 5% of patients are classified as critical.1

percent of mild (81), severe (14) and critical (5) cases of COVID 19.

Figure 1. Based on a study of over 72 000 COVID-19 cases, 81% of people with COVID-19 have mild disease, 14% have severe disease, and 5% of patients are classified as critical.1

The clinical characteristics associated with mild COVID-19

People with mild disease may have mild pneumonia or no signs of pneumonia. They are typically treated at home and the infection resolves with or without supportive care to treat fever or cough or other symptoms as needed.  

Mild pneumonia in lungs, no pneumonia in lungs. Illustration.

Figure 2. People with mild COVID-19 may have mild pneumonia or no signs of pneumonia. 

The clinical characteristics associated with severe COVID-19

Patients with severe disease have breathing problems, problems with oxygenation, and radiological findings. These people will likely be hospitalized. They usually present with breathing problems including dyspnea with a respiratory rate (RR) of 30 or more breaths / min. 

Problems with oxygenation include blood oxygen saturation (SpO2) of 93% or lower, or a P/F ratio of less than 300. On computer tomography (CT), doctors may find lung infiltrates, including ground-glass opacities and consolidations, occupying greater than 50% of the person’s lung fields.2

Clinical characteristics of severe COVID-19 patients. Illustration.

Figure 3. Patients with severe COVID-19 disease have breathing problems, problems with oxygenation, and radiological findings.

The clinical characteristics associated with critical COVID-19

Patients are classified as critical when they present with respiratory failure, septic shock, or multiple organ dysfunction or failure. These patients need to be admitted to the intensive care unit (ICU) and are frequently intubated.

Clinical characteristics of critical COVID-19. Cartoon.

Figure 4. Patients with COVID-19 who are classified as critical present with respiratory failure, septic shock, or multiple organ dysfunction or failure.

 

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Risk factors for COVID-19: Determining the chance of infection and severity of the disease

As the virus continues to spread to a range of populations with different demographics and characteristics, we now have a better idea of who is at risk of becoming infected with COVID-19 and developing severe or critical disease.

Researchers in Iceland studied the likelihood of testing positive for COVID-19 in a high-risk population.3 This population included people who were already symptomatic but did not require hospitalization, and who had recently traveled to a high-risk area or who were in contact with a person who tested positive for COVID-19. The researchers noted that within this high-risk group, men were more likely to test positive for COVID-19 than women, and children had lower chances of testing positive as well. 

Graph of percent of positive COVID-19 cases by age and sex.

Figure 5. Females and children are less likely to test positive for COVID-19. 

Although the likelihood of children testing positive for COVID-19 in this high-risk population was lower than that of adults, the researchers still noted that among the patients under 20 years old, more males tested positive than females, and the chance of becoming infected increased linearly as the children got older. 

graph of fraction of individuals positive for COVID-19 by age and sex.

Figure 6. Even among children, males had a higher chance of testing positive for COVID-19, and the chance of becoming infected increased linearly with age. 

It is still unclear whether the lower incidence of positive results is from less exposure or a biological resistance to the virus. 

 

What increases the chance of death due to COVID-19?

There are a number of factors that put people at risk of dying from COVID-19.

Preexisting medical conditions

Various preexisting medical conditions have been associated with an increased risk of poor COVID-19 outcomes. A large study of over 17 million National Health Service (NHS) patients reported data on risk factors for death from COVID-19 among adults.4

Obesity

Obesity was associated with a 57% increase in dying from COVID-19. When adjusted for confounding factors, the increased risk was 27%. Among patients who have obesity, the risk of dying from COVID-19 rose with an increase in body mass index (BMI). 

Obese patient and risk of death (27%). Cartoon

Figure 7. Obesity increased the risk of death from COVID-19 by 27% (adjusted for confounding factors).

High blood pressure

High blood pressure seems to be a risk factor for dying from COVID-19. In the unadjusted analysis, high blood pressure showed a 22% increased risk of dying from COVID-19. However, when the researchers adjusted the results to account for other confounding factors, the results were no longer significant. 

Female patient with high blood pressure and risk of death. Cartoon

Figure 8. High blood pressure does not increase the risk of death from COVID-19 (adjusted for confounding factors).

Chronic respiratory disease

People with chronic lung diseases had a 135% increased risk of dying from COVID-19, and when adjusted for other confounding factors the increased risk was 78%.

Male patient with chronic lung disease and risk of death (78%). Cartoon

Figure 9. Chronic lung disease increases the risk of death from COVID-19 by 78% (adjusted for confounding factors).

Cardiovascular disease

Patients with cardiovascular disease had a 101% increased risk of dying from COVID-19, but this risk dropped to 27% when adjusted for confounding factors.

Male patient with cardiovascular disease and risk of death (27%). Cartoon

Figure 10. Cardiovascular disease increases the risk of death from COVID-19 by 27% (adjusted for confounding factors). 

Diabetes

Uncontrolled diabetes showed an increased risk of 202%, and when adjusted, the risk was 136%. 

Male patient with diabetes and risk of death (136%). Cartoon

Figure 11. Diabetes increases the risk of death from COVID-19 by 136% (adjusted for confounding factors).

Cancer

If a person was diagnosed with cancer less than one year from contracting COVID-19, their risk of dying from the infection was 83% and dropped to 56% when adjusted. However, if the patient was diagnosed with cancer five or more years ago, the risk of dying from COVID-19 was no longer significant. Hematological cancers also increased a person’s risk of dying from COVID-19, with the risk decreasing as the time from diagnosis increased. However, with hematological cancers, the risk remained significant even if the person was diagnosed five or more years ago.

Female patient with cancer and risk of death (56%). Cartoon

Figure 12. Cancer increases the risk of death from COVID-19 by 56% if diagnosed within the past year (adjusted for confounding factors).

Female patient with hematological cancer and risk of death (252%, 88%). Cartoon

Figure 13. Hematological cancer increases the risk of death from COVID-19 by 252% if diagnosed within the past year, and by 88% if diagnosed more than five years ago (adjusted for confounding factors).

Other preexisting conditions 

People with liver disease, stroke, neurological disorders, kidney disease, organ transplants, and other immunosuppressive conditions also had higher risks of dying from COVID-19.

Other preexisting conditions that confer a higher risk of death due to COVID-19: liver disease, stroke, neurological disorders, kidney disease, organ transplants, immunosuppressive conditions. Illustration.

Figure 14. Other preexisting conditions such as liver disease, stroke, neurological disorders, kidney disease, organ transplants, and other immunosuppressive conditions were also associated with higher risks of dying from COVID-19.

table of common preexisting conditions and the associated increased risk of death due to COVID-19.

Table 1. List of common preexisting conditions increasing the risk of death due to COVID-19.

Ethnic background

The researchers also reported risk factors for dying from COVID-19 across different ethnicities. People from Asian groups had a 95% risk of dying from COVID-19. When adjusted for confounding factors, the increased risk was 62%. Black people also had higher risks of dying from COVID-19, with an unadjusted increased risk of 117%, and an adjusted risk of 71%. 

Female black patient and risk of death (71%) and male Asian patient (62%) Cartoon

Figure 15. The risk of death from COVID-19 varies based on ethnicity with black people having a 71% higher risk of death and Asians having a 62% higher risk of death (adjusted for confounding factors).

What do I do if my patient is considered high-risk?

People in these categories must be monitored closely even if they develop mild symptoms, as they are at higher risk of progressing to a more severe case. Some people may have more than one risk factor, which can further increase their susceptibility to catching SARS-CoV-2 and developing severe disease.

 

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What is the overall mortality rate for COVID-19?

Mortality rates between countries may differ, as testing policies and thresholds for hospitalization vary. Demographics, smoking rates, and the prevalence of comorbidities also impact mortality rates, which vary from country to country. 

In a study of 2634 patients hospitalized with COVID-19 in the New York City area between 1st March and 4th April 2020, the hospitalized mortality rate was 21%.5 Of those patients who died from COVID-19, about 24% were between 18 and 65-years-old. The remaining 76% were all aged over 65 years.

Mortality rate, hospitalized, for patients with COVID 19. Cartoon.

Figure 16. The hospitalized mortality rate for patients with COVID-19 is 21%, with 5% being 18–65-years-old and 16% being 65-years-old.

Looking at it another way, the case fatality rate for hospitalized 18-65-year-olds was 9%, compared to 38% for those over 65-years-old. Mortality rate, hospitalized, for patients with COVID 19. Cartoon.

Figure 17. The hospitalized mortality rate for patients with COVID-19 is 21%, with 5% being 18-65-years-old and 16% being 65-years-old. 

And the case fatality rate increased with the degree of intervention required. For those requiring care in the intensive care unit (ICU), 64% of patients aged 18–65 years died, and 91% of patients over 65-years-old died. 

Case fatality rate for patients with COVID 19 in the ICU. Cartoon.

Figure 18. The case fatality rate of patients with COVID-19 in the ICU: 64% for those 18-65 years old and 91% for those over 65. 

The case fatality rate for those who received mechanical ventilation in the 18–65-year-old age group was 76%; for patients over 65-years-old it was 97%.

Case fatality rate for patients with COVID 19 who are mechanically ventilated. Cartoon.

Figure 19. The case fatality rate of patients with COVID-19 who are mechanically ventilated: 76% for those 18-65-years-old and 97% for those over 65.  

What about children? What's the case fatality rate of COVID-19 in kids?

A study conducted in New York hospitals did not report any deaths under 18 years old, however, severe illness in children is significant albeit less frequent than in adults.6 

Researchers reported the characteristics and outcomes of children with COVID-19 who were admitted to US and Canadian pediatric intensive care units. Researchers collected data from 46 pediatric hospitals, but only 35% of those hospitals reported COVID-19 cases. In total, 48 children were admitted to the ICU, 38% of them required mechanical ventilation, and 4% of the children admitted to the hospital ICU died. This study highlights better hospital outcomes for pediatric patients infected with SARS-CoV-2 since the ICU mortality rates are lower compared with that of adults. 

Case fatatlity rate for hospitalized children with COVID 19. Cartoon.

Figure 20. The case fatality rate for children with COVID-19: 4% of children admitted to hospital with COVID-19 died. 

Further studies may provide additional insight into the clinical characteristics of COVID-19, which can help public health officials design effective strategies to control its spread, and aid clinicians in managing the health consequences of this disease.

 

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References

  1. Wu, Z and McGoogan, JM. 2020. Characteristics of and important lessons from the coronavirus disease 2019 (COVID-19) outbreak in China: Summary of a report of 72 314 cases From the Chinese Center for Disease Control and Prevention. JAMA. 323: 1239–1242. PMID: 32091533
  2. Weiss, P and Murdoch, DR. 2020. Clinical course and mortality risk of severe COVID-19. Lancet. 45: 1014–1015. PMID: 32197108
  3. Gudbjartsson, DF, Helgason, A, Jonsson, H, et al. 2020. Spread of SARS-CoV-2 in the Icelandic population. N Engl J Med. 382: 2302–2315. PMID: 32289214
  4. Williamson, E, Walker, AJ, Bhaskaran, KJ, et al. 2020. OpenSAFELY: factors associated with COVID-19-related hospital death in the linked electronic health records of 17 million adult NHS patients. medRxiv. Doi: 2020.05.06.20092999. Online ahead of print. https://doi.org/10.1101/2020.05.06.20092999
  5. Richardson, S, Hirsch, JS, Narasimhan, M, et al. 2020. Presenting characteristics, comorbidities, and outcomes among 5700 patients hospitalized with COVID-19 in the New York City area. JAMA. 323: 2052–2059. PMID: 32320003
  6. Shekerdemian, LS, Mahmood, NR, Wolfe, KK, et al. 2020. Characteristics and outcomes of children with coronavirus disease 2019 (COVID-19) infection admitted to US and Canadian pediatric intensive care units. JAMA Pediatr. 174: 1–6. PMID: 32392288

Recommended reading

  • Gandhi, RT, Lynch, JB, and Del Rio, C. 2020. Mild or moderate Covid-19. N Engl J Med. doi: 10.1056/NEJMcp2009249. Online ahead of print. PMID: 32329974
  • Grasselli, G, Zangrillo, A, Zanella, A, et al. 2020. Baseline characteristics and outcomes of 1591 patients infected with SARS-CoV-2 admitted to ICUs of the Lombardy region, Italy. JAMA. 323: 1574–1581. PMID: 32250385
  • Onder, G, Rezza, G, and Brusaferro, S. 2020. Case-fatality rate and characteristics of patients dying in relation to COVID-19 in Italy. JAMA. 323: 1775–1776. PMID: 32203977