Respiratory Viruses

 

Clinical Background

Viral respiratory tract infections are the most common diseases affecting humans throughout the world.

Epidemiology

  • Incidence
    • More than 5 million children under the age of 6 experience lower respiratory tract infections (LRTI) each year in the U.S.
    • Between 50-90% of LRTIs in children are caused by viruses
    • Viruses are the fourth leading cause of hospital-treated pneumonia in otherwise healthy adults
  • Age – bimodal peaks
    • Children <10 years
    • Adults >55 years

Organisms

  • Although a wide variety of viral agents are capable of causing LRTI in adults and children, respiratory syncytial virus (RSV), adenovirus, influenza A and B, and parainfluenza 1, 2, and 3 cause 80-90% of LRTIs
    • RSV and influenza are viruses associated with significant annual morbidity and mortality, and which have available therapies
      • RSV causes 50-90% of bronchiolitis infections and 5-40% of pneumonitis infections in children
      • Influenza can cause significant disease in adults and children

Risk Factors

  • Age – <2 years or >55 years
  • Compromised immune system
  • Preexisting chronic medical condition (cardiac, pulmonary, hepatic)

Clinical Presentation

  • Clinical presentation often does not distinguish viruses
    • Nonspecific symptoms of cough, fever, sore throat, rhinorrhea, hoarseness, bronchitis, croup and bronchiolitis
  • Complications
    • Infants, the elderly, and individuals with compromised cardiac, pulmonary or immune systems are at greatest risk for serious complications from LRTI
      • Severe viral pneumonia
      • Acute respiratory failure
      • Secondary bacterial pneumonia