Neisseria meningitidis, often referred to as meningococcus, is a gram negative bacterium that can cause meningitis
and other forms of meningococcal disease such as meningococcemia, a life-threatening sepsis. About 10% of adults are carriers of the bacteria in their nasopharynx. As an exclusively human pathogen it is the main cause of bacterial meningitis in children and young adults, causing developmental impairment and death in about 10% of cases. It causes the only form of bacterial meningitis known to occur epidemically, mainly in Africa and Asia. N. meningitidis is spread through saliva and respiratory secretions during coughing, sneezing, kissing, and chewing on toys. It infects the cell by sticking to it with long thin extensions called pili and surface-exposed proteins and has several virulence factors.