TABLE 1-2.

Clinical Features of Typical and Atypical Common Community-Acquired Pneumonias

	Pneumococcal	Mycoplasma	Viral
Causative agent	Streptococcus pneumoniae	Mycoplasma pneumoniae	Influenza virus A and B
Fever	Sustained 102–103°F	100–103°F	100–103°F unremitting
Chills	Abrupt onset	In 25%	Chilly sensation not rigors
Cough	Productive	Dry, nonproductive	Nonproductive to productive
Sputum	Purulent, blood-stained, rusty	Mucoid, if present	Scant to purulent, may be blood-stained
Gram stain	Diplococci, lance-shaped, often intracellular	No organisms, many alveolar macrophages	No organisms
Chest x-ray	Lobar consolidation	Diffuse perihilar, patchy infiltrates	Diffuse interstitial, perihilar infiltrates
Typical patient	All ages, high incidence in the elderly and alcoholics	Usually children and young adults	Severe illness in elderly
Complications	Meningitis, empyema	Anemia, Steven–Johnson syndrome, myringitis	Staphylococcal infection