Purulent paranasal sinusitis, otitis media, mastoiditis, and bacterial pneumonia are frequent and often serious complications of the common respiratory diseases. These conditions are true bacterial infections. Pneumococci, staphylococci, and streptococci are the chief offenders. Secondary bacterial infection should be suspected if fever increases or leukocytosis occurs, as explained by A.E. Feller in Viral Infections of the Respiratory Tract.
Several other conditions are often considered to be complications of common respiratory disease. Copious, thick nasal exudate, postnatal discharge, laryngitis, hoarseness, aphonia, and chronic cough productive of mucoid or mucopurulent sputum occur so frequently, either during the acute illness or as the acute
process begins to subside, that they may well be integral part of the clinical picture. Painful involvement of the paranasal sinuses during the acute illness seems in many instances properly to be regarded as an extension of the original inflammatory process. There is much uncertainty about a role of bacteria as “secondary invaders” in these conditions.Herpes of the lips or face is particularly frequent in the common cold group. However, in primary atypical
pneumonia, herpes is so unusual that its presence strongly suggests a bacterial etiology of pneumonia.Relatively little is known about the complications in nonbacterial tonsillitis or pharyngitis. There is as yet no indication that they differ appreciably from those which occur with the common cold or acute undifferentiated respiratory disease groups.
Complications of primary atypical pneumonia are unusual. Pleural effusion is rare and when it occurs is almost invariably small, bacteriologically sterile, and readily absorbed. Bacterial complications are carditis occasionally occurs in severe cases and may lead to a fatal outcome. Hemolytic anemia may occur during the acute illness. Numerous other complications have been described but are exceedingly unusual.
The primary site of involvement in the common cold is the upper respiratory passages, principally the nasal mucosa and frequently the lining membranes of the paranasal sinuses. Historically, there are edema, hyperemia, and moderate infiltration with mononuclear cells and granulocytes. Superficial necrosis and desquamation of epithelial cells ensues.