EPIDEMIOLOGY: Sinusitis affects more than 30 million adults in the United States annually.

Direct costs of sinusitis in the US, resulting from medications, outpatient and emergency room visits, and ancillary tests and procedures, are estimated at $3 billion per year. The socioeconomic impact is further magnified by indirect costs from decreased productivity, days lost from work, and impaired quality of life.

PATHOPHYSIOLOGY — The vast majority of cases of acute rhinosinusitis (ARS) are due to viral infection. As noted above, acute bacterial infection occurs in only 0.5 to 2.0 percent of episodes. The most common viruses, determined by maxillary sinus puncture and aspiration, are rhinovirus, influenza virus, and parainfluenza virus.

Acute viral rhinosinusitis (AVRS) begins with viral inoculation via direct contact with conjunctiva or nasal mucosa. Viral replication in a nonimmune individual leads to detectable viral levels in nasal secretions within 8 to 10 hours. Symptoms, if they develop, usually present in the first day after inoculation.

Viral rhinitis spreads to the paranasal sinuses by systemic or direct routes. Nose blowing may be an important mechanism; positive intranasal pressures generated during nose blowing may propel contaminated fluid from the nasal cavity into the paranasal sinuses. Inflammation follows, resulting in sinonasal hypersecretion and increased vascular permeability, followed by transudation of fluid into the nasal cavity and sinuses. Viruses also can exert a direct toxic effect on nasal cilia, impairing mucociliary clearance. A combination of mucosal edema, copious thickened secretions, and ciliary dyskinesia results in sinus obstruction and perpetuates the disease process.

Community-acquired acute bacterial rhinosinusitis (ABRS) occurs when bacteria secondarily infect the inflamed sinus cavity. Although usually occurring as a complication of viral infection, other predisposing conditions associated with acute bacterial sinusitis include allergy, mechanical obstruction of the nose, swimming, odontogenic infection, intranasal cocaine use, impaired mucociliary clearance (eg, cystic fibrosis, cilial dysfunction), immunodeficiency, and other factors that impair sinus drainage.