Meningococcal infection is caused by a bacterium, Neisseria meningitides, or meningococcus. Thirteen serotypes are known, but 4 of them, serotypes A, B, C and W-135, may cause epidemic spread. Although less common, it can cause serious and life-threatening infections including meningitis and septicemia. For every 100 people who contract the infection, up to 15 will die even if they receive proper treatment. Permanent complications of infection include brain damage, deafness, and paralysis of limbs. Meningococcal infection spreads from person to person by coughing, sneezing, or close contact. In Hong Kong, around 5-8 children are diagnosed each year sporadically, with a death rate of around 20%. Serotypes B and C are the most common ones.