Most important source of infection for meningococci:
Case
Subclinical infection
Carriers
Latent case
During periods of endemic disease, about 10% of the general population harbour Neisseria meningitidis in the nasopharynx. 
Since N. meningitidis is a strict human pathogen and most patients have not been in contact with other cases, asymptomatic carriers are presumably the major source of the pathogenic strains.