Complex sentence: It is part of the normal human flora in the nasopharynx in about 10% of adults, and is an exclusively human pathogen, able to cause the only form of bacterial meningitis known to occur epidemically, mainly in Africa and Asia.
Split into simpler sentences: It is part of the normal human flora in the nasopharynx in about 10% of adults. It causes the only form of bacterial meningitis known to occur epidemically, mainly in Africa and Asia.