title: The incidence of primary atypical pneumonia of unknown etiology.
mesh_terms: D006801:Humans; D015994:Incidence; D007251:Influenza, Human; D017563:Lung Diseases, Interstitial; D011014:Pneumonia / Q000453:epidemiology* / Q000706:statistics & numerical data*; D018410:Pneumonia, Bacterial; D011019:Pneumonia, Mycoplasma
keywords: PNEUMONIA/epidemiology and statistics