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For further information, see CMDT Part 32-06: Common Viral Respiratory Infections

Key Features

Essentials of Diagnosis

  • Wide spectrum of symptoms

    • Asymptomatic in at least 20–35% of adults

    • Adults have upper respiratory tract illness with fever and cough most often when symptomatic

    • The clinical triad of cough, fever, and dyspnea is infrequent (< 15%)

    • Advanced pulmonary complications (pneumonia, acute respiratory distress syndrome [ARDS]) with fulminant disease

    • Mortality of 1–21% (varied by geographic area and strain)

  • High predilection for the elderly, the immunocompromised, those with chronic diseases, those living in crowded conditions

General Considerations

  • SARS-CoV-2 shows a higher rate of person-to-person spread than the 2003 SARS-CoV-1 virus

  • Some COVID-19 strains from Western Europe have enhanced transmissibility as a function of a modified Spike protein

  • Transmission

    • R0 is the basic reproductive number signifying the number of persons infected by an infected individual

    • Calculations of R0 for SARS-CoV-2 have varied but the true R0 likely lies somewhere between 2 and 3

    • Presymptomatic spread probably accounts for a large number of cases, since the viral load is highest in the presymptomatic phase

    • The principal mode of transmission is likely respiratory droplets

  • The incubation period for SARS-CoV-2 ranges from 2 to 24 days with an average of about 5 days

  • A clinical risk score calculator to predict critical illness in hospitalized patients with COVID-19 called COVID-GRAM has been validated (

  • SARS-CoV-2 infection is particularly serious in the

    • Elderly

    • Those with comorbid conditions of immunocompromise (including post-organ transplant)

    • Those with chronic diseases (diabetes; obesity; hypertension; chronic heart, lung, or kidney disease; and prior stroke)

Clinical Findings

Symptoms and Signs

  • Most infected individuals are asymptomatic

  • Cough

  • Fever

  • Chills/rigors

  • Myalgias

  • Dyspnea (more common in severe cases)

  • Less common symptoms include

    • Rhinitis

    • Pharyngitis

    • Abdominal symptoms, including nausea and diarrhea

    • Headaches

    • Anosmia

    • Ageusia

  • Symptomatic disease in children is more likely to present with gastrointestinal symptoms and less likely to present with respiratory symptoms

  • Severe COVID-19 likely occurs because of an intense and/or prolonged inflammatory reaction, often called a "cytokine storm"

Differential Diagnosis

  • Seasonal influenza

  • Pneumonia


Laboratory Findings

  • Diagnosis is established using nucleic acid testing

  • Hematologic findings include neutrophilia, absolute lymphopenia, and an increased neutrophil to lymphocyte ratio

  • As disease advances, blood chemistry findings often include elevated liver biochemical tests, and total bilirubin

  • Serum markers of systemic inflammation are increased in most patients with severe infection, including

    • Lactate dehydrogenase level

    • Ferritin

    • C-reactive protein

    • Procalcitonin

    • Interleukin 6 (IL-6)

  • Coagulopathy

    • Identified by elevated von Willebrand factor (VWF) antigen, elevated D-dimer, and fibrin/fibrinogen degradation products

    • Prothrombin time, partial thromboplastin time, and platelet counts are usually unaffected initially


  • Chest radiographs and chest CT ...

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