COVID-19 (summary)

This summary article is intended to be used as a quick reference guide. Please see our complete COVID-19 article for more detail. 

COVID-19 (coronavirus disease 2019) is a viral infectious disease caused by SARS-CoV-2 and is currently a World Health Organizatiοn (WHO) declared pandemic. As of November 2021, over 245 million people had been infected globally with over 5 million deaths ¹³.

Clinical presentation

Many people with SARS-CoV-2 infection are asymptomatic ⁹. Symptoms and signs of COVID-19 are non-specific ¹ but in symptomatic individuals most commonly include:

• fever (85-90%)
• cough (65-70%) with sputum (30-35%)
• smell and taste disturbances (50%) ¹²
• fatigue (35-40%)
• shortness of breath (15-20%)

Complications

The likelihood of severe illness requiring hospitalization correlates closely with male sex, advanced age and presence of comorbidities. 

• ~5% admitted patients require ICU admission

Multiple serious sequelae have been reported including:

• acute respiratory distress syndrome (ARDS)
• coagulopathy: including PE and DIC
• secondary infections, e.g. bacterial pneumonia
• myocardial injury
• sepsis
• acute kidney injury (AKI)
• multiorgan failure
• secondary hemophagocytic lymphohistiocytosis

Pathology

SARS-CoV-2 is a member of the Betacoronavirus genus, one of the genera of the Coronaviridae family of viruses. SARS-CoV-2 is indirectly zoonotic, but transmission is now primarily interhuman. The closest animal coronavirus by genetic sequence is a bat coronavirus ⁵. The cause of death is usually respiratory failure secondary to massive alveolar injury.

Radiographic features

The primary findings of COVID-19 are those of an atypical or organizing pneumonia ^2,3. Up to 18% of cases demonstrate normal chest x-rays or CT when mild/early in the disease course ¹⁰. Bilateral and/or multilobar involvement is common, more often with a lower zone distribution.

Plain radiograph

• patchy or diffuse airspace opacities, whether consolidation or ground-glass opacity ^10,11
• pleural effusion is rare ¹¹

CT

The primary findings on CT chest in adults are ^2,3,16:

• ground-glass opacities (GGO)
• crazy paving appearance (GGOs with septal thickening)
• air space consolidation
• bronchovascular thickening in the lesion
• traction bronchiectasis
• subpleural sparing

Treatment and prognosis

There are several therapeutic approaches: some of them inhibit the replication of the virus, others reduce the inflammatory response (e.g. interleukin inhibitors), whilst others inhibit coagulation ^17,18,22.

Treatment is primarily supportive including mechanical ventilation for some patients. Dexamethasone has been shown to reduce mortality in ventilated patients or those on oxygen therapy ¹⁴.

Several highly-effective vaccines have now received regulatory approval in multiple territories: some of them use mRNA technology; others the technology of the adenoviral vector ^15,20,21. 

The mortality rate is estimated to be 3.6% ¹⁰.

The persistence of disabling symptoms long after the acute illness has resolved has become known as long COVID ¹⁹.

Differential diagnoses

• influenza or parainfluenza virus and other causes of atypical pneumonia ^7,8
• interstitial lung disease (ILD) ⁹
• pulmonary edema ⁷