RESPIRATORY INFECTIONS
The respiratory tract includes the nose, throat, bronchial tubes leading to the lungs, and
the lungs. Closely associated with the system are the paranasal sinuses and the middle ear. The most common infections are viral infections of the upper respiratory tract, for example, the nose and the throat. The common cold, viral pharyngitis, and bronchitis are annoying, but rarely serious, illnesses.
Occasionally, however, bacterial infections may supervene, and the illness may become more severe. Bacterial infections of the middle ear may, if untreated, result in loss of hearing. Infections of the sinuses occasionally lead to infection of the brain and surrounding structures.
Streptococcal pharyngitis is of importance mainly because of the sequelae that may follow. Patients who suffer from untreated streptococcal disease may develop complications such as rheumatic fever (an inflammation of various organs, most prominently the heart valves) or inflammation of the kidneys.
More serious respiratory system disorders involve the lungs. Bacterial pneumonias, especially those caused by the pneumococcus and the staphylococcus, are common and serious diseases. Tuberculosis and the fungal diseases such as histoplasmosis and coccidioidomycosis may also involve the lungs. Infections of the lungs may damage tissue and cause chronic scarring and impairment of respiratory activity. In acute infections, death resulting from interference with normal gas exchange may occur. Patients with underlying lung diseases such as chronic bronchitis, an irritative condition associated with smoking and air pollution, are more susceptible to pulmonary infections.