National Center for Biotechnology Information NCBI NLM MEDLINE diagnosis humans pubmed abstract nih national institutes of health national library of medicine adult female male adolescent middle aged Incidence Causality acute disease differential bacterial* / cerebrospinal fluid meningitis bacterial* / epidemiology pmid:9046894 doi:10.1001/archinte.1997.00440250077009 b sigurdardóttir o m björnsson s gudmundsson iceland / epidemiology bacterial* / complications bacterial* / diagnosis bacterial* / microbiology bacterial* / mortality bacterial* / therapy