History:
Background: Upper respiratory infections are common infections and include pharyngitis, sinusitis, epiglottitis, laryngotracheitis, and the common cold. Viruses play a significant role in the pathogenesis of many of these infections. Bacteria and other organisms also are responsible.
Pharyngitis is an inflammatory process of the pharynx, hypopharynx, uvula, and tonsils that can be caused by viral or bacterial infection and, occasionally, both. Distinguishing between these infections is important because rheumatic fever and acute glomerulonephritis may complicate untreated group A beta-hemolytic streptococcal infections (GAS), but they usually can be prevented by appropriate antibiotic treatment.
Sinusitis is an inflammatory process involving the paranasal sinuses (maxillary, frontal, ethmoid, and sphenoid). It usually is a bacterial complication of a viral upper respiratory infection.
Epiglottitis is a life-threatening disease observed most frequently in children aged 1-6 years, often during the fall and winter. Although less common, it also can affect adults.
Laryngotracheitis usually is the result of viral infection. The subglottic area and trachea are involved, whereas the area above the true vocal cords is spared. When children younger than 5 years have the infection, it is called croup.
The common cold is a mild, self-limited, catarrhal syndrome caused, for the most part, by members of 5 families of viruses. A small proportion of colds are complicated by bacterial infections of the paranasal sinuses and the middle ear, which require antimicrobial therapy.
Pathophysiology: In infectious pharyngitis, bacteria or viruses may invade the pharyngeal mucosa directly, causing a local inflammatory response. Other viruses, such as Rhinovirus, cause irritation of pharyngeal mucosa secondary to nasal secretions.
Streptococcal infections are characterized by local invasion and release of extracellular toxins and proteases. In addition, M protein fragments of certain serotypes of GAS are similar to myocardial sarcolemma antigens and are linked to rheumatic fever and subsequent heart valve damage. Acute glomerulonephritis may result from antibody-antigen complex deposition in glomeruli.
The most common local predisposing cause of suppurative sinusitis is a viral upper respiratory tract infection. Inflammation and edema in the ostial meatal complex can obstruct the sinus ostium, leading to hypo-oxygenation of the sinus, disturbed ciliary and mucous blanket function, and diminished local resistance.
In epiglottitis, supraglottic structures become inflamed and edematous, leading to narrowed airway and respiratory compromise. Epiglottitis in children almost always is caused by Haemophilus influenzae type b (HIB). In adults, it frequently is nonbacterial.
Laryngitis mainly affects children and begins with a prodrome of a few days of a mild viral upper respiratory infection. As the infection extends to the proximal trachea, diffuse inflammation with exudate and edema of the subglottic area causes narrowing of the airway. The cricoid ring of the trachea, in the immediate subglottic area, is the narrowest portion of the airway in a child. A small amount of edema can cause significant airway obstruction. Inspiratory stridor occurs when air flows through this narrowed subglottic area.
Infection with common cold viruses characteristically is short in duration and self-limited.
Frequency:
In the US: Children in day care in the United States are estimated to have an upper respiratory infection approximately every 3 weeks from the age of 6 months to 2 years. The incidence then decreases, and, by the time of school entry, a child has about 3-6 episodes of upper respiratory infection per year. Most of these infections include pharyngitis and/or laryngitis. Viral upper respiratory infections frequently occur in mini-epidemics.