Chapter 031. Pharyngitis, Sinusitis, Otitis, and Other Upper Respiratory Tract Infections (Part 1)

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Harrison's Internal Medicine Chapter 31. Pharyngitis, Sinusitis, Otitis, and Other Upper Respiratory Tract Infections Pharyngitis, Sinusitis, Otitis, and Other Upper Respiratory Tract Infections: Introduction Infections of the upper respiratory tract (URIs) have a tremendous impact on public health. They are among the most common reasons for visits to primary care providers, and, although the illnesses are typically mild, their high incidence and transmission rates place them among the leading causes of time lost from work or school. Even though the minority (~25%) of cases are caused by bacteria, URIs are the leading diagnoses for which antibiotics are prescribed on an...

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Chapter 031. Pharyngitis, Sinusitis, Otitis, and Other Upper Respiratory Tract Infections (Part 1) Harrison's Internal Medicine > Chapter 31. Pharyngitis, Sinusitis, Otitis, and Other Upper Respiratory Tract Infections Pharyngitis, Sinusitis, Otitis, and Other Upper Respiratory Tract Infections: Introduction Infections of the upper respiratory tract (URIs) have a tremendous impact on public health. They are among the most common reasons for visits to primary care providers, and, although the illnesses are typically mild, their high incidence and transmission rates place them among the leading causes of time lost from work or school. Even though the minority (~25%) of cases are caused by bacteria, URIs are the leading diagnoses for which antibiotics are prescribed on an outpatient basis in the United States. The enormous consumption of antibiotics for these illnesses has contributed to the rise in antibiotic resistance among common community-acquired pathogens such as Streptococcus pneumoniae—a trend that in itself has had an enormous influence on public health.
Although most URIs are caused by viruses, distinguishing patients with primary viral infection from those with primary bacterial infection is difficult. Signs and symptoms of bacterial and viral URIs are, in fact, indistinguishable. Because routine, rapid testing is neither available nor practical for most syndromes, acute infections are diagnosed largely on clinical grounds. Thus the judicious use of antibiotics in this setting is challenging. Nonspecific Infections of the Upper Respiratory Tract Nonspecific URIs are a broadly defined group of disorders that collectively constitute the leading cause of ambulatory care visits in the United States. By definition, nonspecific URIs have no prominent localizing features. They are identified by a variety of descriptive names, including acute infective rhinitis, acute rhinopharyngitis/nasopharyngitis, acute coryza, and acute nasal catarrh, as well as by the inclusive label common cold. Etiology The large assortment of URI classifications reflects the wide variety of causative infectious agents and the varied manifestations of common pathogens. Nearly all nonspecific URIs are caused by viruses spanning multiple virus families and many antigenic types.
For instance, there are at least 100 immunotypes of rhinovirus (Chap. 179), the most common cause of URI (~30–40% of cases); other causes include influenza virus (three immunotypes; Chap. 180) as well as parainfluenza virus (four immunotypes), coronavirus (at least three immunotypes), and adenovirus (47 immunotypes) (Chap. 179). Respiratory syncytial virus (RSV) also accounts for a small percentage of cases each year, as do some viruses not typically associated with URIs (e.g., enteroviruses, rubella virus, and varicella-zoster virus). Even with sophisticated diagnostic and culture techniques, a substantial proportion (25–30%) of cases have no assigned pathogen. Clinical Manifestations The signs and symptoms of nonspecific URI are similar to those of other URIs but lack a pronounced localization to one particular anatomic location, such as the sinuses, pharynx, or lower airway. Nonspecific URI is commonly described as an acute, mild, and self-limited catarrhal syndrome, with a median duration of ~1 week. Signs and symptoms are diverse and frequently variable across patients.
The principal signs and symptoms of nonspecific URI include rhinorrhea (with or without purulence), nasal congestion, cough, and sore throat. Other manifestations, such as fever, malaise, sneezing, and hoarseness, are more variable, with fever more common among infants and young children. Occasionally, clinical features reflect the underlying viral pathogen; myalgias and fatigue, for example, are sometimes seen with influenza and parainfluenza infections, while conjunctivitis may suggest infection with adenovirus or enterovirus. Findings on physical examination are frequently nonspecific and unimpressive. Between 0.5 and 2% of colds are complicated by secondary bacterial infections (e.g., rhinosinusitis, otitis media, and pneumonia), particularly in high-risk populations such as infants, elderly persons, and chronically ill patients. Secondary bacterial infections are usually associated with a prolonged course of illness, increased severity of illness, and localization of signs and symptoms. Purulent secretions from the nares or throat have often been used as an indication of sinusitis or pharyngitis. However, these secretions are also seen in nonspecific URI and, in the absence of other clinical features, are poor predictors of bacterial infection.