Neisseria meningitidis, Serogroup A

**Definition:** Strains of Neisseria meningitidis responsible for most outbreaks of meningococcal disease in Western Europe and the United States in the first half of the 20th century. They continue to be a major cause of disease in Asia and Africa, and especially localized epidemics in Sub-Sahara Africa.

**Tree numbers:** - B03.440.400.425.550.550.641.700 - B03.660.075.525.520.500.700

**Synonyms:** - Meningococcus, Serogroup A - Meningococci, Serogroup A