National Center for Biotechnology Information NCBI NLM MEDLINE humans pubmed abstract nih national institutes of health national library of medicine research support non-u.s. gov't female male adolescent Child preschool Multicenter Study Incidence Family Characteristics drug resistance multiple africa south of the sahara / epidemiology fever / etiology fever / microbiology vera von kalckreuth florian marks typhoid fever / epidemiology* salmonella infections / epidemiology* salmonella infections / microbiology pmid:28193398 pmc5316558 doi:10.1016/s2214-109x(17)30022-0 thomas f wierzba salmonella* / isolation & purification typhoid fever / microbiology