Neisseria meningitidisis an aerobic, Gram-negative diplococcus that colonizes the nasopharynx of many healthy individuals. Microbial and host factors combine to allow this organism to invade the bloodstream and get into the central nervous system, causing severe sepsis and meningitis. Hypervirulent strains may be transmitted from person to person through respiratory secretions, causing outbreaks of meningococcal disease. Several areas of the world, especially sub-Saharan Africa, have hyperendemic meningococcal disease. In the United States, most cases are sporadic; only approximately 2 percent of cases occur as outbreaks. However, outbreak-related cases have greater morbidity and mortality than sporadic cases. Patients with meningococcal disease should be promptly identified, and Droplet Precautions should be started when the diagnosis is initially suspected. Household contacts and individuals with direct exposure to patients' respiratory secretions require the administration of chemoprophylaxis. Five meningococcal serogroups cause the majority of cases: A, B, C, Y, and W-135; quadrivalent (A, C, Y, and W-135) polysaccharide and conjugate vaccines are available and recommended for populations at highest clinical or epidemiological risk of developing invasive meningococcal disease.