COVID-19
COVID-19 Definition
  • COVID-19, caused by the SARS-CoV-2 virus, is a viral respiratory illness ranging from asymptomatic or mild upper respiratory tract symptoms to severe pneumonia, respiratory failure, and multi-organ dysfunction. It primarily spreads through respiratory droplets and can lead to systemic inflammation, affecting multiple organ systems.
Epidemiology, Risk Factors & Prevention
  • COVID-19 Clinical Epidemiology
  • Risk Factors: Older age (≥65 years), male sex, obesity, smoking, and underlying conditions such as diabetes, cardiovascular disease, chronic respiratory disease, and immunosuppression increase the risk of severe disease. Socioeconomic factors, including crowded living conditions and healthcare access, also impact risk.
  • Prevention: Vaccination remains the most effective prevention strategy, reducing severity and transmission. Other measures include wearing masks in high-risk settings, maintaining good hand hygiene, and social distancing during outbreaks. Early testing and isolation help prevent community spread, and antiviral prophylaxis may be considered for high-risk individuals.
COVID-19 Pathophysiology
  • The SARS-CoV-2 virus binds to ACE2 receptors, which are abundant in the respiratory tract and other organs such as the heart, kidneys, and gastrointestinal system. This leads to viral replication, triggering local and systemic inflammation. In severe cases, a hyperinflammatory response, known as a “cytokine storm”, leads to ARDS (acute respiratory distress syndrome), multi-organ failure, and sometimes death.
COVID-19 Time Course
  • Incubation Period: Typically 2-14 days after exposure.
  • Acute Phase: Lasts 7-14 days, during which symptoms emerge, peaking at days 5-7.
  • Recovery Phase: For mild cases, resolution occurs in 10-14 days. For severe cases, patients may progress to a critical phase with prolonged symptoms and recovery over weeks to months.
COVID-19 Symptoms
  • Fever – Common due to systemic inflammatory response to viral replication and immune system activation.
  • Cough – Dry or productive; results from irritation of respiratory tract and viral-induced inflammation.
  • Fatigue – General malaise often due to the body’s immune response and systemic inflammation.
  • Dyspnoea – Shortness of breath in moderate to severe cases, due to alveolar inflammation and decreased oxygen exchange.
  • Anosmia and Ageusia – Loss of smell and taste, often early signs, likely due to viral effects on the olfactory nerve or central nervous system involvement.
  • Headache – Likely secondary to systemic inflammation and cytokine release.
COVID-19 Signs
  • Tachypnoea – Increased respiratory rate due to respiratory distress or decreased oxygenation.
  • Hypoxia – Low oxygen saturation in moderate to severe cases, due to impaired gas exchange in inflamed lungs.
  • Fever – Elevated body temperature as a systemic response to infection.
  • Crackles on lung auscultation – Resulting from fluid or inflammation in alveoli, indicative of pneumonia or ARDS.
  • Confusion or altered mental status – Seen in severe cases, possibly due to hypoxia or cytokine effects on the central nervous system.
COVID-19 Red Flag Features
  • Severe Dyspnoea – Suggests worsening respiratory failure or ARDS.
  • Chest Pain – May indicate myocarditis, a severe complication of COVID-19.
  • Confusion/Altered Consciousness – Could signify hypoxia, encephalopathy, or multi-organ failure.
  • Persistent Hypoxia – Indicates worsening respiratory compromise, necessitating urgent intervention.
  • Cyanosis – Suggests critical oxygen depletion, requiring immediate management.
COVID-19 Atypical Presentations
  • Asymptomatic – Particularly common in young, healthy individuals, despite viral shedding.
  • Gastrointestinal Symptoms – Diarrhoea, nausea, and vomiting in some cases, due to viral replication in the gastrointestinal tract.
  • Thromboembolic Events – Including deep vein thrombosis (DVT) and pulmonary embolism (PE), due to increased clotting risk in severe COVID-19.
  • “Happy Hypoxia” – Severe hypoxia without significant dyspnoea or distress, often seen in COVID-19 pneumonia.
COVID-19 Diagnostic Tests
  • RT-PCR – Gold standard for COVID-19 diagnosis; detects viral RNA in respiratory samples.
  • Lateral Flow Test – Rapid antigen detection, useful for screening but less sensitive than PCR.
  • Chest X-ray – In severe cases, may show bilateral infiltrates consistent with pneumonia or ARDS.
  • CT Chest – Shows “ground-glass opacities” and consolidations in severe cases.
  • Blood Tests – Raised CRP, D-dimer, and ferritin levels indicate systemic inflammation and hypercoagulability; lymphopenia is common.
COVID-19 Problem Representation
  • A 55-year-old male presents with a 5-day history of fever, cough, and progressive shortness of breath. He has a history of hypertension. Oxygen saturation is 89% on room air, with bilateral crackles on lung auscultation.
COVID-19 Differential Diagnosis
  • Influenza – Similar presentation but typically has a shorter incubation period and lacks anosmia.
  • Community-acquired pneumonia – Often more abrupt onset, with focal rather than diffuse lung findings.
  • Pulmonary Embolism – May present with dyspnoea, but without fever or upper respiratory symptoms.
  • Acute Heart Failure – Can present with dyspnoea and crackles, but typically has a cardiac history and no infectious symptoms.
COVID-19 Treatment
  • Supportive Care – Includes oxygen supplementation for hypoxia and fluids to maintain hydration.
  • Corticosteroids (e.g., Dexamethasone) – Recommended in severe cases requiring oxygen or ventilatory support to reduce inflammation.
  • Antiviral Therapy (e.g., Remdesivir) – Reserved for early severe cases, particularly in those hospitalised or at high risk of deterioration.
  • Monoclonal Antibodies – For patients at high risk of severe disease to prevent progression.
  • Anticoagulation – For those with high D-dimer levels or at risk of thromboembolic events.
COVID-19 Complications
  • Acute Respiratory Distress Syndrome (ARDS) – Occurs in severe cases due to overwhelming lung inflammation.
  • Thromboembolism – Increased risk of DVT and PE, due to hypercoagulability seen in severe COVID-19.
  • Myocarditis – Direct viral infection or inflammatory response affecting the heart.
  • Long COVID – Prolonged symptoms, such as fatigue and dyspnoea, lasting weeks to months post-infection.

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