From the NIH: Haemophilus influenzae type B meningitis can occur in children with natural exposure to only a small number of organisms.
D000367:Age Factors; D000818:Animals; D001769:Blood / Q000382:microbiology; D002555:Cerebrospinal Fluid / Q000382:microbiology; D002675:Child, Preschool; D006193:Haemophilus influenzae / Q000302:isolation & purification; D006801:Humans; D008583:Meningitis, Haemophilus / Q000382:microbiology*; D009666:Nose / Q000382:microbiology; D010614:Pharynx / Q000382:microbiology; D051381:Rats