Infection is most common in the winter and spring months.
Meningococcal disease primarily affects very young children. However, it does occur in young adults, in males more than females, and more commonly in newly gathered adults living in crowded conditions, such as in barracks and college dormitories. Group A organisms are responsible for disease in the subSaharan region of Africa. During the 1990s, Group B has been the most common cause of disease in the Americas, and there have been outbreaks in Cuba, Brazil, Chile, Argentina and Colombia . Community outbreaks of group C disease, affecting school and college-aged youths, have been occurring with increasing frequency in Canada and the United States since 1990.