Upper Respiratory Tract Infection
Rhinitis is the most common manifestation of the common cold (Table S–8). It is characterized by variable fever, inflammatory edema of the nasal mucosa, and an increase in mucous secretions. The net result is varying degrees of nasal obstruction; the nasal discharge may be clear and watery at the onset of illness, becoming thick and sometimes purulent as the infection progresses over 5 to 10 days.
TABLE S–8Major Infectious Causes of Upper Respiratory Disease ||Download (.pdf) TABLE S–8 Major Infectious Causes of Upper Respiratory Disease
|DISEASE ||VIRUSES ||BACTERIA AND FUNGI |
|Rhinitis ||Rhinoviruses, adenoviruses, coronaviruses, parainfluenza viruses, influenza viruses, respiratory syncytial virus, some coxsackie A viruses ||Rare |
|Pharyngitis or tonsillitis ||Adenoviruses, parainfluenza viruses, influenza viruses, rhinoviruses, coxsackie A or B virus, herpes simplex virus, Epstein-Barr virus ||Group A streptococci, Corynebacterium diphtheriae, Neisseria gonorrhoeae |
|Peritonsillar or retropharyngeal abscess ||None ||Group A streptococci (most common), oral anaerobes such as Fusobacterium species, Staphylococcus aureus, Haemophilus influenzae (usually in infants) |
Pharyngitis and tonsillitis are associated with pharyngeal pain (sore throat) and the clinical appearance of erythema and swelling of the affected tissues. There may be exudates, consisting of inflammatory cells overlying the mucous membrane, and petechial hemorrhages; the latter may be seen in viral infections but tend to be more prominent in bacterial infections. Viral infections, particularly herpes simplex, may also lead to the formation of vesicles in the mucosa, which quickly rupture to leave ulcers.
Peritonsillar or retrotonsillar abscesses are usually a complication of tonsillitis. They are manifested by local pain, and examination of the pharynx reveals tonsillar asymmetry with one tonsil usually displaced medially by the abscess. This infection is most common in children older than 5 years and in young adults.
Retropharyngeal or lateral pharyngeal abscesses occur most frequently in infants and children under 5 years of age. They can result from pharyngitis or from accidental perforation of the pharyngeal wall by a foreign body. The infection is characterized by pain, inability or unwillingness to swallow, and, if the pharyngeal wall is displaced anteriorly near the palate, a change in phonation (nasal speech).
Middle Respiratory Tract Infection
Epiglottitis is often characterized by the abrupt onset of throat and neck pain, fever, and inspiratory stridor (difficulty in moving adequate amounts of air through the larynx) (Table S–9). Because of the inflammation and edema in the epiglottis and other soft tissues above the vocal cords (supraglottic area), phonation becomes difficult (muffled phonation or aphonia), and the associated pain leads to difficulty in swallowing.
TABLE S–9Major Causes of Acute Middle Respiratory Tract Disease ||Download (.pdf) TABLE S–9 Major Causes of Acute Middle Respiratory Tract Disease
|SYNDROME ||VIRUSES ||BACTERIA ||PERCENTAGE CAUSED BY VIRUSES |
|Epiglottitis ||Rare ||Haemophilus influenzae, Streptococcus pneumoniae, Corynebacterium diphtheriae, Neisseria meningitidis ||<10 |
|Laryngitis and croup ||Parainfluenza viruses, influenza viruses, adenoviruses; occasionally respiratory syncytial virus, metapneumovirus, rhinoviruses, coronaviruses, echoviruses ||Rare ||90 |
|Tracheitisa ||Same as for laryngitis and croup ||H influenzae, Staphylococcus aureus ||90 |
|Bronchitis and bronchiolitis ||Parainfluenza viruses, influenza viruses, respiratory syncytial virus, adenoviruses measles ||Bordetella pertussis, H influenzae, Mycoplasma pneumoniae, Chlamydia pneumoniae ||80 |
Laryngitis or its more severe form, croup, may have an abrupt onset (spasmodic croup) or may develop more slowly over hours or a few days as a result of spread of infection from the upper respiratory tract. The illness is characterized by variable fever, inspiratory stridor, hoarse phonation, and a harsh, barking cough. In contrast to epiglottitis, the inflammation is localized to the subglottic laryngeal structures, including the vocal cords. It sometimes extends to the trachea (laryngotracheitis) and bronchi (laryngotracheobronchitis), where it is associated with a deeper, more severe cough that may provoke chest pain and variable degrees of sputum production.
Bronchitis or tracheobronchitis may be a primary manifestation of infection or a result of spread from upper respiratory tissues. It is characterized by cough, variable fever, and sputum production, which is often clear at the onset but may become purulent as the illness persists. Auscultation of the chest with the stethoscope often reveals coarse bubbling rhonchi, which are a result of inflammation and increased fluid production in the larger airways.
Chronic bronchitis is a result of longstanding damage to the bronchial epithelium. A common cause is cigarette smoking, but a variety of environmental pollutants, chronic infections (eg, tuberculosis), and defects that hinder normal clearance of tracheobronchial secretions and bacteria (eg, cystic fibrosis) can be responsible. Because of the lack of functional integrity of their large airways, such patients are susceptible to chronic infection with members of the oropharyngeal microbiota and to recurrent, acute flare-ups of symptoms when they become colonized and infected by viruses and bacteria.
Lower Respiratory Tract Infection
Acute pneumonia is an infection of the lung parenchyma that develops over hours to days and, if untreated, runs a natural course lasting days to weeks (Table S–10). The onset may be gradual, with malaise and slowly increasing fever, or sudden, as with the bed-shaking chill associated with the onset of pneumococcal pneumonia. The only early symptom referable to the lung may be cough, which is caused by bronchial irritation. In adults, the cough becomes productive of sputum, which is purulent material generated in the alveoli and small air passages. In some cases, the sputum may be blood-streaked, rusty in color, or foul smelling.
TABLE S–10Major Causes of Lower Respiratory Tract Infection ||Download (.pdf) TABLE S–10 Major Causes of Lower Respiratory Tract Infection
|SYNDROME ||VIRUSES ||COMMON BACTERIA ||FUNGI ||OTHER AGENTS |
|Acute pneumonia ||Influenza,a parainfluenza, adenovirus, respiratory syncytial virus (infants and elderly)a metapneumovirus ||Streptococcus pneumoniae, Staphylococcus aureus, Haemophilus influenzae, Enterobacteriaceae, Legionella, mixed anaerobes (aspiration), Pseudomonas aeruginosab ||Candida albicans,b Aspergillus species Pneumocystisb ||Mycoplasma pneumoniae, Chlamydia trachomatis (infants), Chlamydia pneumoniae |
|Chronic pneumonia ||Rare ||Mycobacterium tuberculosis, other mycobacteria, Nocardia ||Coccidioides immitis,c ||Paragonimus westermanic |
| || || ||Blastomyces dermatitidis,c || |
| || || ||Histoplasma capsulatum,c || |
| || || ||Cryptococcus neoformans || |
|Lung abscess ||None ||Mixed anaerobes, Actinomyces, Nocardia, S aureus,d Enterobacteriaceae,d P aeruginosab,d ||Aspergillus species ||Entamoeba histolytica |
|Empyema ||None ||Mixed anaerobes, S aureus,d S pneumoniae,d Enterobacteriaceae, P aeruginosad ||Rare || |
Chronic pneumonia has a slow insidious onset that develops over weeks to months and may last for weeks or even years. The initial symptoms are the same as those of acute pneumonia (fever, chills, and malaise), but they develop more slowly. Cough can develop early or late in the illness. As the disease progresses, appetite and weight loss, insomnia, and night sweats are common. Cough and sputum production may be the first indication of a vague constitutional illness referable to the lung. Bloody sputum (hemoptysis), dyspnea, and chest pain appear as the disease progresses. There may be parenchymal destruction and the formation of abscesses or cavities communicating with the bronchial tree.
Pleural effusion is the transudation of fluid into the pleural space in response to an inflammatory process in adjacent lung parenchyma. It may result from a wide variety of causes, both infectious and noninfectious.
Empyema is a purulent infection of the pleural space that develops when the infectious agent gains access by contiguous spread from an infected lung through a bronchopleural fistula or, less often, by extension of an abdominal infection through the diaphragm. Symptoms are usually insidious and related to the primary infection until enough exudate is formed to produce symptoms referable to the chest wall or to compromise the function of the lung.
Lung abscess is usually a complication of acute or chronic pneumonia caused by organisms that can cause localized destruction of lung parenchyma. It may occur as part of a chronic process or as an extension of an acute, destructive pneumonia, often after aspiration of oral or gastric contents. The symptoms of lung abscess, which are usually not specific, resemble those of chronic pneumonia or an acute pneumonia that has failed to resolve. Persistent fever, cough, and the production of foul-smelling sputum are typical.
The examination of expectorated sputum has been the primary means of diagnosing the causes of bacterial pneumonia, but this approach has several advantages and disadvantages. The advantages are ease of collection and absence of risk to the patient. The primary disadvantage is the confusion that results from contamination of the sputum with oropharyngeal microbiota in the process of expectoration and excessive contamination with saliva. Microscopic examination before culture of direct Gram smears of specimens alleged to be sputum has proved useful. Polymorphonuclear leukocytes (PMNs) and large numbers of a single morphologic type of organism are typical findings in sputum from patients with bacterial pneumonia. Squamous epithelial cells from the oropharynx and a mixed bacterial population are characteristic of saliva. Another approach is to attempt a more direct collection from the lung using methods that bypass the oropharyngeal flora. This approach may be used in patients who are not producing sputum or in cases where analysis of expectorated sputum has been inconclusive. The major techniques include transtracheal aspiration, bronchoalveolar lavage (BAL), direct aspiration, and open lung biopsy.