Waning immunity among the population against a particular strain favours epidemics, as do overcrowding and climatic conditions such as dry seasons or prolonged drought and dust storms. Smoking, mucosal lesions and concomitant respiratory infections are considered risk factors that may contribute to the development of the disease. The disease mainly affects young children, but is also common in older children and young adults.
The disease occurs sporadically throughout the world with seasonal variations and accounts for a proportion of endemic bacterial meningitis. However, the highest burden of the disease is due to the cyclic epidemics occurring in the African meningitis belt.
