Reproduced with kind permission of Group B Strep Support.
GBS colonises up to 30% of adults in the UK, without symptoms or side-effects. However, GBS can also cause infection, most commonly in newborn babies before, during or shortly after birth. GBS can more rarely cause infection in adults (typically women during pregnancy or after birth, the elderly and people with serious underlying medical conditions which impair their immune system).

GBS is also a recognised cause of preterm delivery, maternal infections, stillbirths and late miscarriages. GBS infections are rare in adults, especially so for men and women who are not pregnant.
Overall, without preventative medicine, GBS infections affect an estimated 1 in every 1,000 babies born in the UK. Each year, based on 700,000 babies born annually in the UK, approximately:
230,000 babies are born to mothers who carry GBS; 88,000 babies, 1 in every 8, become colonised with GBS; 700 babies develop GBS infections, usually within 2 days of birth; and 75 babies (10% of infected babies) die.
Of the survivors of GBS meningitis, up to a third suffer long-term mental and/or physical handicaps, from mild learning disabilities to severe mental retardation, loss of sight, loss of hearing and lung damage (in around 12% of the survivors, the disabilities may be severe). The great majority of survivors of early-onset disease do so with no long-term damage.