primary atypical pneumonia n any of a group of pneumonias (as Q fever and psittacosis) caused esp. by a virus, mycoplasma, rickettsia, or chlamydia
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a general term applied to any of numerous acute infectious pulmonary diseases, formerly referring to any type other than bacterial pneumonia; causative organisms include Mycoplasma pneumoniae (see mycoplasmal p.), species of Rickettsia, Chlamydophila, and Chlamydia, and various viruses (see viral p.). All are marked by extensive but tenuous pulmonary infiltration and by fever, malaise, myalgia, sore throat, and a cough that at first is nonproductive but becomes productive and paroxysmal. Called also atypical, atypical bronchial, or cold agglutinin p.Medical dictionary. 2011.