Meningococcal disease

Neisseria meningitidis is a Gram-negative diplococcus and exclusively human pathogen that can cause meningitis and other manifestations such as meningococcemia, a life-threatening sepsis ^[1]. Disease-causing strains are classified by the antigenic structure of their polysaccharide capsule, with six serogroups (A, B, C, W, X, Y) accounting for most global cases ^[1][2].

Initial illness commonly presents with nonspecific symptoms such as fatigue, fever, and headache, and may rapidly advance to neck stiffness, coma, or death in roughly 10% of cases ^[1]. Petechiae appear in about half of patients, and meningococcal meningitis symptoms can be readily confused with those from other bacterial pathogens ^[1]. The organism adheres to host cells via pili and surface proteins Opa and Opc and employs several virulence factors ^[1].

N. meningitidis is a leading cause of bacterial meningitis and septicaemia worldwide, with high case fatality and long-term impairment among survivors ^[2]. It causes the only epidemically occurring bacterial meningitis, mainly in Africa and Asia, and is endemic and epidemic globally ^[1]. In the United States about 2,500 to 3,500 infections occur yearly (≈1 per 100,000), with highest incidence in infants and elevated risk in children under five and high-school-age adolescents ^[1]. African meningitis belt rates were as high as 1–10 per 1,000 before 2010 vaccination, and invasive disease incidence has broadly declined via immunization and secular trends ^[1][2].

The bacterium spreads through saliva and respiratory secretions during coughing, sneezing, kissing, sharing toys, or common fresh-water sources ^[1]. Transmission via oral sex causing urethritis in men has also been reported ^[1]. Approximately 10% of adults carry the organism asymptomatically in the nasopharynx ^[1].

Adolescent immunization schedules include quadrivalent meningococcal conjugate vaccine and, for higher-risk individuals or via shared decision-making, serogroup B vaccines ^[3]. Conjugate vaccines against serogroups A, C, W, and Y have markedly reduced respective disease burdens, with serogroup C nearly eliminated in UK childhood following infant and catch-up campaigns ^[2][4]. Invasive disease is rare but frequently vaccine-preventable, though evaluation of direct vaccine effectiveness is limited by low incidence and relies on serological correlates ^[5].

1. 1 Wikipedia contributors. Neisseria meningitidis - Wikipedia [Internet]. Wikipedia. cited 3 Sept 2026. Available from: https://en.wikipedia.org/wiki/Neisseria_meningitidis
2. 2 Parikh SR et al. The everchanging epidemiology of meningococcal disease worldwide and the potential for prevention through vaccination. J Infect. 2020 Oct. PMID: 32504737. doi: 10.1016/j.jinf.2020.05.079. PubMed: https://pubmed.ncbi.nlm.nih.gov/32504737/
3. 3 Bernstein HH et al. The Need to Optimize Adolescent Immunization. Pediatrics. 2017 Mar. PMID: 28167517. doi: 10.1542/peds.2016-4186. PubMed: https://pubmed.ncbi.nlm.nih.gov/28167517/
4. 4 Bethell D et al. Meningococcal vaccines. Expert Rev Vaccines. 2002 Jun. PMID: 12908514. doi: 10.1586/14760584.1.1.75. PubMed: https://pubmed.ncbi.nlm.nih.gov/12908514/
5. 5 Findlow J et al. A review of complement sources used in serum bactericidal assays for evaluating immune responses to meningococcal ACWY conjugate vaccines. Hum Vaccin Immunother. 2019. PMID: 30883271. doi: 10.1080/21645515.2019.1593082. PubMed: https://pubmed.ncbi.nlm.nih.gov/30883271/