Meningococcal disease
![Meningitis bacteria, SEM. © Science Photo Library](https://www.ecdc.europa.eu/sites/default/files/styles/is_large/public/images/Meningococcal-disease_H.jpg?itok=DmsodBBs)
Meningococcal disease is caused by the bacterium Neisseria meningitidis. The bacterium is often detected in the nasopharynx without causing disease, a situation described as asymptomatic carriage. The bacteria occasionally invade the body and cause meningococcal infection, which is an acute severe bacterial infection. Invasive meningococcal disease (IMD) is a major cause of meningitis and septicaemia. The disease often has a rapid progression, with an 8–15% case-fatality ratio. The highest incidence occurs in young children, with a second disease peak among adolescents and young adults.