What Are Considered Upper Respiratory Tract Infections?
Upper respiratory tract infections (URIs) are acute infections affecting the nose, sinuses, pharynx (throat), and larynx (voice box), and include common cold, pharyngitis, acute sinusitis, acute otitis media, and laryngitis. 1, 2
Specific Conditions Classified as URIs
Core URI Entities
- Common cold (nasopharyngitis): Inflammatory syndrome of the upper pharynx (cavum) with varying degrees of nasal inflammation, typically viral in origin 1, 3
- Acute pharyngitis: Infection of the throat, predominantly viral, though approximately 15% may be caused by Group A beta-hemolytic streptococcus 4, 5
- Acute sinusitis (rhinosinusitis): Inflammation of the sinus cavities, often associated with the common cold 1, 2
- Acute otitis media: Middle ear infection, particularly common in children 1, 2
- Laryngitis and laryngotracheitis: Infections of the voice box and windpipe 5, 3
Key Anatomical Boundaries
- URIs affect structures from the mouth through the trachea (windpipe), distinguishing them from lower respiratory tract infections which involve the bronchi and lungs 3
- The FDA defines upper respiratory tract infections as involving the ear, nose, and throat 6
Clinical Characteristics That Define URIs
Typical Presentation
- Nasal symptoms: Congestion, discharge (which may be purulent), postnasal drip 1
- Throat symptoms: Throat clearing, pharyngeal discomfort (though not prominent in nonspecific URIs) 1
- Systemic symptoms: Low-grade fever, headache, malaise 1
- Cough: Often present but not the dominant feature (distinguishes from lower respiratory infections) 1
Duration and Natural History
- Most uncomplicated URIs resolve spontaneously within 1-2 weeks 1, 7
- Patients typically feel better within the first week 1, 7
- Viral sinusitis associated with colds resolves within 21 days without antibiotics 1
Critical Distinction: Viral vs. Bacterial
Predominantly Viral Origin
- The vast majority (>80-90%) of acute URIs are caused by viruses 1, 4
- At least 200 identified viruses can cause the common cold syndrome, including rhinoviruses, coronaviruses, parainfluenza viruses, respiratory syncytial virus, adenoviruses, and enteroviruses 1
- Up to 90% of viral upper respiratory infections show CT evidence of sinus involvement, yet these resolve without antibiotics 1
When Bacterial Infection Should Be Suspected
- Acute bacterial sinusitis follows only 0.5% to 13% of viral URIs 1
- Bacterial complications such as bacterial rhinosinusitis or pneumonia are rare 1
- Purulent nasal discharge and sputum do NOT predict bacterial infection and patients with these symptoms do not benefit from antibiotics 1, 7
Common Pitfall to Avoid
The presence of colored or purulent secretions does not indicate bacterial infection. 1, 7 This is one of the most important clinical pearls—colonization of airways by bacteria enhanced by viral infection does not equate to bacterial superinfection requiring antibiotics in healthy adults. 1 The onset of purulent sputum during acute URI is not associated with bacterial superinfection. 1