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Pneumonia, Viral
Tomás Franquet, MD, PhD
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KEY FACTS

  • Terminology

    • Imaging

      • Top Differential Diagnoses

        • Clinical Issues

          • Diagnostic Checklist

            TERMINOLOGY

            • Definitions

              • Pulmonary viral infection typically affects respiratory epithelium from trachea to terminal bronchioles
                • Alveolar involvement less common, but often severe and rapidly progressive
            • RNA Virus-Related Diseases

              • Influenza
                • Seasonal community infections, endemic infections, and unpredictable pandemics
                • Influenza type A: Most important respiratory virus affecting general population with regards to morbidity and mortality
                • Major cause of respiratory illness in immunocompromised hosts
              • Avian influenza (H5N1)
                • Contact with infected birds; usually poultry
                • Overall case fatality rate exceeds 60%
              • Swine influenza (H1N1)
                • 1st pandemic of 21st century, originally reported in Mexico (spring of 2009)
                • High transmission among humans, but virulence not greater than that observed with seasonal influenza
              • Parainfluenza virus
                • Common cause of seasonal upper respiratory tract infection in adults and children
                • Parainfluenza virus type 3: Respiratory illness in immunocompromised hosts and solid organ transplant recipients
              • Respiratory syncytial virus (RSV)
                • Ubiquitous cause of respiratory infection
                • Most frequent viral cause of lower respiratory tract infection in infants
              • Human metapneumovirus (hMPV)
                • Implicated in 4-21% of infants with acute bronchiolitis
                  • Symptoms clinically indistinguishable from those elicited by RSV
                • 4% of cases among patients with community-acquired pneumonia (CAP) or chronic obstructive pulmonary disease (COPD) exacerbations
              • Measles
                • One of 3 major infectious diseases worldwide
                  • 1.5 million childhood deaths per year
              • Coxsackievirus, echovirus, and enterovirus
                • Lower respiratory tract infection may occur sporadically and is not always associated with pneumonia
              • Human T-lymphotropic virus type 1 (HTLV-1)
                • Etiologic retrovirus of adult T-cell leukemia or lymphoma
                  • Associated with myelopathy, Sjögren syndrome, and lymphocytic pneumonitis
              • Hantavirus
                • Rodent-borne zoonotic disease
                  • Hantavirus pulmonary syndrome: Severe acute respiratory distress syndrome (ARDS), rapid clinical progression, and high mortality
              • Severe acute respiratory syndrome (SARS)
                • Atypical pneumonia caused by newly discovered SARS-associated coronavirus (SARS-CoV) in 2012 (Guangdong, China)
              • Middle east respiratory syndrome (MERS)
                • Acute viral respiratory disease caused by novel virus currently named MERS coronavirus (MERS-CoV)
            • DNA Viruses

              • Adenovirus
                • 5-10% of acute respiratory infections in infants and children, but < 1% of respiratory illnesses in adults
                • Swyer-James-MacLeod syndrome: Acquired constrictive bronchiolitis due to childhood adenovirus infection
              • Varicella virus
                • Common contagious infection in childhood, increasing frequency in adults
                  • Varicella pneumonia: 1 of every 400 cases of adulthood chickenpox infection
              • Cytomegalovirus (CMV)
                • CMV infection: > 70% of hematopoietic stem cell transplant (HSCT) recipients; ~ 1/3 develop CMV pneumonia
                  • Infection during postengraftment period (30-100 days after transplantation)
              • Epstein-Barr virus (EBV)
                • Primary infection manifests as infectious mononucleosis
                • EBV pneumonia: Rare in immunocompetent or immunocompromised subjects
                • Associated with development of Burkitt lymphoma, Hodgkin lymphoma, nasopharyngeal carcinoma

            IMAGING

            • Radiographic Findings

              • CT Findings

                DIFFERENTIAL DIAGNOSIS

                  PATHOLOGY

                  • Microscopic Features

                    CLINICAL ISSUES

                    • Presentation

                      • Demographics

                        • Natural History & Prognosis

                          DIAGNOSTIC CHECKLIST

                          • Consider

                            • Image Interpretation Pearls

                              Selected References

                              1. Franquet T: Imaging of pulmonary viral pneumonia. Radiology. Jul;260(1):18-39, 2011
                              2. Kim EA et al: Viral pneumonias in adults: radiologic and pathologic findings. Radiographics. 22 Spec No:S137-49, 2002
                              Related Anatomy
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                              Related Differential Diagnoses
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                              References
                              Tables

                              Tables

                              KEY FACTS

                              • Terminology

                                • Imaging

                                  • Top Differential Diagnoses

                                    • Clinical Issues

                                      • Diagnostic Checklist

                                        TERMINOLOGY

                                        • Definitions

                                          • Pulmonary viral infection typically affects respiratory epithelium from trachea to terminal bronchioles
                                            • Alveolar involvement less common, but often severe and rapidly progressive
                                        • RNA Virus-Related Diseases

                                          • Influenza
                                            • Seasonal community infections, endemic infections, and unpredictable pandemics
                                            • Influenza type A: Most important respiratory virus affecting general population with regards to morbidity and mortality
                                            • Major cause of respiratory illness in immunocompromised hosts
                                          • Avian influenza (H5N1)
                                            • Contact with infected birds; usually poultry
                                            • Overall case fatality rate exceeds 60%
                                          • Swine influenza (H1N1)
                                            • 1st pandemic of 21st century, originally reported in Mexico (spring of 2009)
                                            • High transmission among humans, but virulence not greater than that observed with seasonal influenza
                                          • Parainfluenza virus
                                            • Common cause of seasonal upper respiratory tract infection in adults and children
                                            • Parainfluenza virus type 3: Respiratory illness in immunocompromised hosts and solid organ transplant recipients
                                          • Respiratory syncytial virus (RSV)
                                            • Ubiquitous cause of respiratory infection
                                            • Most frequent viral cause of lower respiratory tract infection in infants
                                          • Human metapneumovirus (hMPV)
                                            • Implicated in 4-21% of infants with acute bronchiolitis
                                              • Symptoms clinically indistinguishable from those elicited by RSV
                                            • 4% of cases among patients with community-acquired pneumonia (CAP) or chronic obstructive pulmonary disease (COPD) exacerbations
                                          • Measles
                                            • One of 3 major infectious diseases worldwide
                                              • 1.5 million childhood deaths per year
                                          • Coxsackievirus, echovirus, and enterovirus
                                            • Lower respiratory tract infection may occur sporadically and is not always associated with pneumonia
                                          • Human T-lymphotropic virus type 1 (HTLV-1)
                                            • Etiologic retrovirus of adult T-cell leukemia or lymphoma
                                              • Associated with myelopathy, Sjögren syndrome, and lymphocytic pneumonitis
                                          • Hantavirus
                                            • Rodent-borne zoonotic disease
                                              • Hantavirus pulmonary syndrome: Severe acute respiratory distress syndrome (ARDS), rapid clinical progression, and high mortality
                                          • Severe acute respiratory syndrome (SARS)
                                            • Atypical pneumonia caused by newly discovered SARS-associated coronavirus (SARS-CoV) in 2012 (Guangdong, China)
                                          • Middle east respiratory syndrome (MERS)
                                            • Acute viral respiratory disease caused by novel virus currently named MERS coronavirus (MERS-CoV)
                                        • DNA Viruses

                                          • Adenovirus
                                            • 5-10% of acute respiratory infections in infants and children, but < 1% of respiratory illnesses in adults
                                            • Swyer-James-MacLeod syndrome: Acquired constrictive bronchiolitis due to childhood adenovirus infection
                                          • Varicella virus
                                            • Common contagious infection in childhood, increasing frequency in adults
                                              • Varicella pneumonia: 1 of every 400 cases of adulthood chickenpox infection
                                          • Cytomegalovirus (CMV)
                                            • CMV infection: > 70% of hematopoietic stem cell transplant (HSCT) recipients; ~ 1/3 develop CMV pneumonia
                                              • Infection during postengraftment period (30-100 days after transplantation)
                                          • Epstein-Barr virus (EBV)
                                            • Primary infection manifests as infectious mononucleosis
                                            • EBV pneumonia: Rare in immunocompetent or immunocompromised subjects
                                            • Associated with development of Burkitt lymphoma, Hodgkin lymphoma, nasopharyngeal carcinoma

                                        IMAGING

                                        • Radiographic Findings

                                          • CT Findings

                                            DIFFERENTIAL DIAGNOSIS

                                              PATHOLOGY

                                              • Microscopic Features

                                                CLINICAL ISSUES

                                                • Presentation

                                                  • Demographics

                                                    • Natural History & Prognosis

                                                      DIAGNOSTIC CHECKLIST

                                                      • Consider

                                                        • Image Interpretation Pearls

                                                          Selected References

                                                          1. Franquet T: Imaging of pulmonary viral pneumonia. Radiology. Jul;260(1):18-39, 2011
                                                          2. Kim EA et al: Viral pneumonias in adults: radiologic and pathologic findings. Radiographics. 22 Spec No:S137-49, 2002