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COVID

Clinical Subject Page

COVID

COVID-19 pneumonia is a viral lung infection caused by SARS-CoV-2. It occurs when the virus infects the lungs, causing inflammation that can make it difficult to breathe.

Also called

Coronavirus disease 2019

ICD-10

U07.1

Specialty

Pulmonology

Onset

Acute

Reviewed

July 2026

On This Page

Overview

  • Caused by the SARS-CoV-2 virus
  • Spread mainly through respiratory fluids
  • Disease severity ranges from:
    • Mild illness
    • Viral pneumonia
    • Severe pneumonia with low oxygen levels
    • Critical illness with respiratory failure and organ dysfunction

Etiology & Risk Factors

–Cause: Infection with SARS-CoV-2 (COVID-19 virus).

  • Transmission: Mainly through exposure to respiratory fluids (droplets and aerosols).

-Risk Factors (for severe Cases)

  • Older age (especially ≥ 65 years)
  • Chronic lung disease
  • Heart disease
  • Diabetes mellitus
  • Chronic kidney or liver disease
  • Obesity (BMI ≥ 30)
  • Cancer
  • Immunosuppression
  • Smoking
  • Pregnancy or recent pregnancy

Pathophysiology

SARS-CoV-2 infection → Binds to ACE2 receptors on lung cells → Virus enters cells (TMPRSS2 activation) → Viral replication → Direct damage to alveolar cells → Immune activation and cytokine release → Lung inflammation → Fluid in alveoli and impaired oxygen exchange → Hypoxemia → (Severe cases) Cytokine storm → ARDS, organ failure, and possible death

Clinical Presentation

  • Presentation

    • Fever
    • Cough (usually dry)
    • Shortness of breath (dyspnea)
    • Fatigue
    • Sore throat
    • Headache
    • Muscle aches (myalgia)
    • Loss of smell and/or taste
    • Runny nose (rhinitis)
    • Nausea, vomiting, or diarrhea (may occur)

    Severe presentation:

    • Marked shortness of breath
    • Low oxygen saturation (hypoxemia)
    • Respiratory failure (critical cases)

History Taking

    • When did your symptoms start?
    • Do you have a fever?
    • Do you have a cough? Is it dry or productive?
    • Are you short of breath?
    • Do you have chest pain?
    • Have you lost your sense of smell or taste?
    • Do you have a sore throat or runny nose?
    • Have you had contact with anyone who has COVID-19 or is sick?
    • Have you tested positive for COVID-19?
    • Do you have any chronic illnesses (e.g., diabetes, heart or lung disease)?
    • Have you received a COVID-19 vaccination?
    • Do you smoke?

Physical Examination

-General examination

  • Fever
  • Tachypnea (rapid breathing)
  • Low oxygen saturation (SpO₂)
  • Respiratory distress (in severe cases)

 

-Respiratory examination

  • Crackles (crepitations) on auscultation
  • Decreased breath sounds
  • Dullness to percussion (if consolidation)
  • Increased tactile fremitus and egophony (with consolidation)

 

–Severe signs

    • Hypoxemia
    • Respiratory failure

Assess:
• Respiratory status
• Hemodynamic stability
• Oxygen saturation
• Signs of respiratory distress
Perform an ABCDE assessment in unstable patients

Investigations

  • RT-PCR – confirms COVID-19 (gold standard)
  • Rapid antigen test – quick screening test
  • CBC – assess blood cell count
  • CRP ± ESR – assess inflammation
  • ABG – if severe disease or low oxygen
  • Pulse oximetry (SpO₂) – check oxygen saturation
  • Chest X-ray – look for lung infiltrates/opacities
  • Chest CT – if chest X-ray is inconclusive or to assess severity
  • RT-PCR confirms the diagnosis.
  • Chest X-ray/CT assess pneumonia severity but cannot diagnose on their own.

Diagnosis

-Diagnosis is based on:

Clinical features (fever, cough, shortness of breath)

  • Positive RT-PCR (gold standard) or rapid antigen test
  • Chest X-ray or CT showing pneumonia (lung infiltrates/opacities)
  • Diagnosis  is confirmed by viral testing; imaging supports the diagnosis and assesses disease severity.
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Related Topics

Management of COVID

  • Isolation and infection control
  • Supportive care: rest, fluids, nutrition
  • Antipyretics/analgesics for fever and pain
  • Oxygen therapy if hypoxemic
  • Remdesivir (selected patients)
  • Dexamethasone for patients requiring supplemental oxygen
  • Anticoagulation (LMWH) for hospitalized patients unless contraindicated
  • Mechanical ventilation if respiratory failure develops
  • Treatment depends on disease severity. Mild cases usually need supportive care, while severe cases may require oxygen, medications, and intensive care.

Complications of COVID

  • Hypoxemic respiratory failure
  • Acute respiratory distress syndrome (ARDS)
  • Septic shock
  • Thromboembolic events (e.g., pulmonary embolism, ischemic stroke)
  • Acute kidney injury (AKI)
  • Cardiac complications (heart failure, ischemic heart disease, arrhythmias)
  • Long COVID

The most important life-threatening complications are hypoxemic respiratory failure, ARDS, and septic shock.

Prognosis of COVID

  • Most patients recover completely, especially with mild disease.
  • Prognosis is worse in older adults and those with underlying medical conditions.
  • Risk of death increases with age.
  • Vaccination and booster doses reduce the risk of severe disease and death.

Key Points / Clinical Pearls of COVID

  • It is a viral lung infection caused by SARS-CoV-2.
  • It mainly presents with fever, dry cough, and shortness of breath.
  • Diagnosis is confirmed by RT-PCR or antigen testing, while chest X-ray or CT helps assess the severity of pneumonia.
  • Most mild cases need supportive care
  • severe cases may require oxygen, medications, and hospitalization.
  • Serious complications include hypoxemic respiratory failure, ARDS, septic shock, and thromboembolism.
  • Early diagnosis, prompt treatment, and vaccination improve outcomes.