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INTRODUCTION

Meningococcal disease, due to the bacterium Neisseria meningitidis (meningococcus), is a serious cause of bacterial meningitis and sepsis globally. The high mortality and epidemic potential of meningococcal disease have led to extensive prevention and control efforts.

BACTERIOLOGY

N. meningitidis is an aerobic, gram-negative bacterium that is closely related to other Neisseria species including N. gonorrhoeae and commensal organisms such as N. lactamica. The outer membrane proteins and polysaccharide capsule are important virulence factors that help the bacterium attach to the naso- and oropharyngeal epithelium and evade phagocytosis and complement-mediated lysis.1 N. meningitidis is classified into 12 serogroups based on characteristics of the polysaccharide capsule, with serogroups A, B, C, W, X, and Y the most common causes of meningococcal disease worldwide.2

EPIDEMIOLOGY

Meningococcal disease occurs globally, though the incidence and serogroup distribution varies by region. Average annual incidence in recent years has ranged from <0.10 cases per 100,000 population in parts of Latin America and Asia to 7.5 cases per 100,000 population in areas of the meningitis belt of sub-Saharan Africa.3,4 In the United States, incidence has steadily declined since the late 1990s, with an incidence of 0.11 cases per 100,000 population in 2017.5 In many regions of the world, incidence of meningococcal disease is highest in infants and young children, followed by a peak in incidence in adolescents, who have the highest rates of asymptomatic oropharyngeal carriage, and thus are thought to be the primary sources of transmission to other groups.6,7 Globally, serogroup B and C cause a significant burden of invasive disease, though in recent years several regions have experienced rapid expansion of a serogroup W clone.2,8 Serogroup A was historically the primary cause of the high rates of endemic meningococcal disease and large-scale epidemics in sub-Saharan Africa.9 A variety of meningococcal vaccination strategies have been implemented globally, further influencing the epidemiology of disease in vaccinated areas over time.10

Outbreaks of meningococcal disease can occur in community settings or may affect persons in organization-based settings, such as schools, universities, childcare facilities, or healthcare facilities. Outbreaks are relatively uncommon in the United States, accounting for approximately 5% of all cases.11 In recent years, several serogroup B meningococcal disease outbreaks at universities and serogroup C outbreaks among men who have sex with men have been reported in the United States.11,12 In other areas of the world, outbreaks are a significant cause of morbidity and mortality. In the “meningitis belt” of sub-Saharan Africa, periodic large-scale epidemics occur every 5–10 years, with incidence rates as high as 1000 cases per 100,000 population.9 Following introduction of a serogroup A meningococcal conjugate vaccine starting in 2010, large serogroup A epidemics were eliminated in this region, though several large outbreaks due to serogroups C and W have been reported, along with increased incidence of serogroup ...

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