COVID-19
COVID-19 is the respiratory illness caused by SARS-CoV-2, a positive-sense RNA coronavirus that binds ACE2 receptors, ranging from asymptomatic infection to hypoxemic pneumonia and acute respiratory distress syndrome. Diagnosis relies on RT-PCR of a nasopharyngeal sample, and hospitalized hypoxemic patients are treated with dexamethasone plus remdesivir, escalating to baricitinib or tocilizumab and thromboprophylaxis.
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What this article covers
- Overview
Coronavirus disease 2019 (COVID-19) is the clinical syndrome caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), a positive-sense RNA coronavirus first identified in Wuhan, China, in December 2019.
- Epidemiology
Transmission: Spread occurs by respiratory droplets, aerosols, and less commonly fomites, with prolonged, close, indoor contact carrying the highest risk.
- Risk factors
Older age: Age 65 years or older is the strongest single predictor of progression to severe disease.
- Pathophysiology
The SARS-CoV-2 spike glycoprotein binds ACE2 on airway and alveolar epithelial cells, type II pneumocytes, vascular endothelium, and enterocytes, explaining the combination of respiratory, vascular, and gastrointestinal manifestations.
- Clinical features
Onset: Fever, dry cough, sore throat, nasal congestion, myalgia, headache, and fatigue follow the incubation period; nausea, vomiting, and diarrhea occur in a meaningful minority.
- Differential diagnosis
Influenza: Overlapping fever, myalgia, and cough, but anosmia and ageusia are far less prominent; a multiplex respiratory viral panel distinguishes the two.
- Diagnosis
Establishing the diagnosis: Confirmed by a positive reverse transcription polymerase chain reaction (RT-PCR) for SARS-CoV-2 RNA from a nasopharyngeal sample, the preferred initial test and the most…
- Management
First action, mild or asymptomatic disease: Manage at home with supportive care (antipyretics, analgesics, oral hydration) and isolation for 5 to 10 days, stopping once the patient has been afebrile…
- Complications
ARDS and respiratory failure: The dominant cause of death, developing about a week after symptom onset in patients who progress.
- Prognosis
Most infections are mild and resolve fully without hospitalization.
- Prevention
Vaccination: Recommended for everyone age 6 months and older; updated formulations and booster doses lower the risk of hospitalization and death, and pregnant and lactating patients may be vaccinated.
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Influenza is an acute orthomyxoviral respiratory illness with abrupt fever, myalgia, and cough, driven by an H and N surface glycoprotein antigenicity that drifts yearly (seasonal epidemics) and occasionally shifts (pandemics). Diagnosis is clinical or confirmed by nucleic acid amplification testing, and neuraminidase-inhibitor or endonuclease-inhibitor antiviral therapy started within 48 hours of onset shortens illness and reduces complications in high-risk patients.
- Community-acquired pneumonia
Community-acquired pneumonia is a lower respiratory tract infection acquired outside the hospital that is diagnosed by a compatible clinical syndrome plus a new infiltrate on chest imaging, risk-stratified with CURB-65 or the Pneumonia Severity Index to guide site of care, and treated with empiric antibiotics chosen by site of care and comorbidity, escalating to cover MRSA or Pseudomonas aeruginosa when risk factors are present.
- Acute respiratory distress syndrome (ARDS)
ARDS is acute (within 1 week), bilateral, non-cardiogenic hypoxemic respiratory failure from diffuse alveolar damage, diagnosed by the 2012 Berlin criteria and graded by the Pao2/Fio2 ratio. Management is lung-protective ventilation, PEEP titration, early prone positioning for severe disease, conservative fluid strategy, and treatment of the inciting insult.
- Pulmonary embolism
Pulmonary embolism is thrombus, usually from a lower-extremity deep vein thrombosis, obstructing the pulmonary arterial circulation and causing V/Q mismatch, right ventricular strain, and hypoxemia. Diagnosis follows Wells criteria (with PERC in low-risk patients) to sequence D-dimer, CT pulmonary angiography, and V/Q scanning, and management is risk-stratified anticoagulation escalating to thrombolysis or embolectomy for hemodynamic instability.
- Pneumocystis jirovecii pneumonia
Pneumocystis jirovecii pneumonia is a subacute, often hypoxic pneumonia in patients with CD4 counts below 200/mcL or comparable immunosuppression, diagnosed by organism visualization on induced sputum or bronchoalveolar lavage and treated with 21 days of high-dose trimethoprim-sulfamethoxazole plus adjunctive steroids when hypoxic.
- Bordetella pertussis (whooping cough)
Whooping cough is a highly infectious bronchitis caused by the gram-negative coccobacillus Bordetella pertussis, marked by catarrhal, paroxysmal, and convalescent stages with lymphocytosis; diagnosis is clinical, confirmed by nasopharyngeal PCR, and treated with azithromycin plus prophylaxis of close contacts.
- Sepsis
Sepsis is life-threatening organ dysfunction caused by a dysregulated host response to infection, identified by an acute rise in SOFA score of 2 points or more in a patient with known or suspected infection. Survival depends on recognizing the pattern early and completing the hour-1 bundle: lactate, blood cultures before antibiotics, broad-spectrum antibiotics such as cefepime 2 g IV every 8 hours, and 30 mL/kg crystalloid for hypotension or a lactate of 4 mmol/L or higher.