Incidence in the USA is around 10,000 to 15,000 non-fatal cases per year, and the pattern of incidence is thought to be cyclic, with peaks every few years. About one third of all women will be infected by this bacterium at some time in their lifetime, but often they have no symptoms. The group B [Streptococcus] bacterium is a leading cause of death among newborne infants in the USA. It infects around 8,000 babies each year, killing about 500 and leaving the rest with severe brain damage from menigitis.