National Center for Biotechnology Information NCBI NLM MEDLINE Teaching humans pubmed abstract nih national institutes of health national library of medicine logistic models prognosis research support non-u.s. gov't adult female male age factors adolescent aged middle aged Comorbidity Prospective Studies 80 and over follow-up studies severity of illness index chi-square distribution pneumonia multivariate analysis hospitalization hospitals odds ratio survival rate community-acquired infections / epidemiology* community-acquired infections / etiology bacterial / etiology bacterial / classification haemophilus influenzae pmid:11083685 doi:10.1378/chest.118.5.1344 c m luna a famiglietti r j gené argentina / epidemiology chlamydophila infections / classification chlamydophila infections / epidemiology chlamydophila pneumoniae community-acquired infections / classification epidemiologic studies haemophilus infections / classification haemophilus infections / epidemiology bacterial / epidemiology* mycoplasma / classification mycoplasma / epidemiology pneumococcal / classification pneumococcal / epidemiology