National Center for Biotechnology Information NCBI NLM MEDLINE humans pubmed abstract nih national institutes of health national library of medicine adult female male age factors adolescent middle aged sex factors Incidence community-acquired infections / drug therapy pneumonia hospitalization bacterial / drug therapy bacterial / microbiology* cities community-acquired infections / microbiology* finland / epidemiology bacterial / epidemiology viral / epidemiology viral / drug therapy viral / mortality demography bacterial / mortality community-acquired infections / mortality viral / virology* survivors pmid:11283803 doi:10.1086/319746 c jokinen l heiskanen p h mäkelä community-acquired infections / virology*