Infectious Disease · Viral Respiratory Infections
The facts most likely to be tested
The SARS-CoV-2 virus utilizes the angiotensin-converting enzyme 2 (ACE2) receptor for cellular entry via the spike protein.
Nirmatrelvir/ritonavir (Paxlovid) is the preferred antiviral treatment for non-hospitalized patients at high risk for progression to severe disease.
Dexamethasone is the standard of care for hospitalized patients requiring supplemental oxygen or mechanical ventilation to reduce mortality.
Multisystem inflammatory syndrome in children (MIS-C) presents as a post-infectious hyperinflammatory state with persistent fever, elevated inflammatory markers, and multiorgan involvement.
Reverse transcription-polymerase chain reaction (RT-PCR) remains the gold standard diagnostic test due to its high sensitivity and specificity.
Venous thromboembolism (VTE) and pulmonary embolism are common hypercoagulable complications requiring prophylactic anticoagulation in hospitalized patients.
Acute respiratory distress syndrome (ARDS) is the primary cause of mortality, characterized by diffuse alveolar damage and refractory hypoxemia.
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A 68-year-old male with a history of type 2 diabetes and hypertension presents to the emergency department with 5 days of fever, dry cough, and progressive dyspnea. His oxygen saturation is 89% on room air. Physical examination reveals bilateral crackles on lung auscultation. A chest X-ray demonstrates bilateral peripheral ground-glass opacities. The patient is hemodynamically stable but requires 3L of oxygen via nasal cannula to maintain saturation >92%.
Which of the following is the most appropriate pharmacologic intervention to reduce mortality in this patient?
Dexamethasone
This patient has severe COVID-19 requiring supplemental oxygen; systemic corticosteroids like dexamethasone are indicated to reduce mortality in patients requiring respiratory support.
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High yield triage
Etiology / Epidemiology
Caused by SARS-CoV-2; highly transmissible via respiratory droplets. Advanced age and immunocompromise are primary risk factors.
Clinical Manifestations
Fever, dry cough, and anosmia are classic. Hypoxemia without dyspnea is a hallmark silent hypoxia.
Diagnosis
RT-PCR is the gold standard. SpO2 < 94% on room air indicates severe disease.
Treatment
Nirmatrelvir/ritonavir for mild-moderate high-risk; Dexamethasone for hospitalized patients requiring oxygen.
Prognosis
Most recover; ARDS and thromboembolism are the leading causes of mortality.
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Epidemiology & Etiology
SARS-CoV-2 is a positive-sense single-stranded RNA virus. Transmission occurs primarily through respiratory aerosols. Obesity, diabetes, and chronic kidney disease significantly increase the risk of progression to severe disease.
Pertinent Anatomy
The virus targets the ACE2 receptor, which is highly expressed in the alveolar type II pneumocytes. This localization explains the primary pulmonary involvement and subsequent respiratory failure.
Pathophysiology
Viral entry triggers a massive release of pro-inflammatory cytokines, known as a cytokine storm. This leads to diffuse alveolar damage, microvascular thrombosis, and systemic endothelial dysfunction. The resulting hypercoagulable state increases the risk of pulmonary embolism and stroke.
Clinical Manifestations
Patients present with fever, fatigue, and dry cough. Anosmia and ageusia are highly specific early indicators. Dyspnea at rest, persistent chest pain, and confusion are red flags requiring immediate hospitalization.
Diagnosis
RT-PCR of nasopharyngeal swab is the diagnostic gold standard. Chest imaging often reveals bilateral peripheral ground-glass opacities. Pulse oximetry showing SpO2 < 94% is the clinical threshold for supplemental oxygen initiation.
Treatment
Outpatient management for high-risk patients includes Nirmatrelvir/ritonavir (Paxlovid). Hospitalized patients requiring oxygen receive Dexamethasone and prophylactic anticoagulation. Do not use hydroxychloroquine or ivermectin as they lack clinical efficacy.
Prognosis
Complications include ARDS, secondary bacterial pneumonia, and multisystem inflammatory syndrome. Patients must be monitored for thromboembolic events even after clinical recovery.
Differential Diagnosis
Influenza: typically presents with more abrupt onset and prominent myalgias
Bacterial pneumonia: usually associated with lobar consolidation and productive cough
RSV: more common in pediatric populations with wheezing
Pulmonary Embolism: sudden onset dyspnea without preceding viral prodrome
Heart Failure: elevated BNP and peripheral edema distinguish from viral pneumonitis