Neisseria meningitidis is an exclusively human pathogen that has evolved primarily to colonize the nasopharynx rather than to cause systemic disease.

Nontypeable Haemophilus influenzae is a major cause of localized respiratory tract disease and initiates infection by colonizing the nasopharynx.

Because meningococcus is a mucosal pathogen colonizing the nasopharynx, local mucosal immune responses may play an important role in host defense against infection and carriage.