Viral respiratory tract infections are the most common diseases affecting humans worldwide. Respiratory viruses can be associated with both self-limiting upper respiratory tract infections (e.g., the common cold) and more severe lower respiratory tract infections (e.g., bronchitis, bronchiolitis, pneumonitis, pneumonia).
Lower respiratory tract infections are a major cause of hospitalization, morbidity, and mortality in infants and the elderly. Respiratory infections are common and generally cause self-limited illnesses in healthy, immunocompetent hosts. Although respiratory illnesses are frequently mild, viruses may cause significant morbidity and mortality in immunocompromised hosts (e.g., transplant recipients, and patients with underlying malignancies).
Viral infections cause about 80% of respiratory tract diseases. Mixed infections account for 20 percent of infections in adults and 60% in children. The symptomatic disease varies by viral type and patient age. The highest rates of viral infections occur in young and elderly populations. Seasonal influenza constitutes a large proportion of viral respiratory infections. Symptoms generally occur within 1-3 days of exposure and last 7-14 days.
Symptoms of upper respiratory infections include:
- Nasal congestion
- Sneezing
- Cough
- Sore throat
- Fever
- Chills
- Fatigue
- Decreased appetite (especially in children)
- Lethargy (especially in children)
Symptoms of lower respiratory infections include:
- Worsening cough
- Shortness of breath
- Focal pain
- Dizziness (older adults)
- Confusion (older adults)
Viral culture, once the gold standard method for the detection of respiratory viruses, is slow and labor-intensive and requires specialized expertise, while rapid antigen detection methods are faster but generally suffer from low sensitivity (immunochromatography, rapid tests).
Multiplex molecular assays, which rely on the detection of viral nucleic acids, provide prompt results with high sensitivity and specificity, making them ideal tests when used in the context of a thoughtful clinical evaluation.
