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

Pharyngitis, Sinusitis, Otitis, and Other Upper Respiratory Tract Infections Part 1 Harrison's Internal Medicine > Chapter 31.. Pharyngitis, Sinusitis, Otitis, and Other Upper Respirat

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