What is group B Strep?

//What is group B Strep?
What is group B Strep? 2017-09-10T16:35:13+00:00

Group B Streptococcus (GBS or group B Strep) is a normal bacterium which is carried by 20-40% of adults, most commonly in the gut, and for around 25% of women, in the vagina, usually without symptoms or side-effects.

GBS can occasionally cause serious infection, most commonly in newborn babies, sometimes in adults and, very rarely, during pregnancy and before labour.

GBS is not a sexually transmitted disease. Treatment of a woman and her partner carrying GBS does not prevent re-colonisation.

Group B Strep Infection in Newborn babies

There are two types of group B Strep infection in newborns: early and late-onset.

Early-onset GBS infection is more common (2/3 of cases in babies) and occurs when the baby is up to 6 days old; a key symptom is the rapid development of breathing problems, associated with blood poisoning.

Late-onset GBS infection – usually presenting as GBS meningitis – occurs between age 7 days and 1 month and, more rarely, up to age 3 months. After 3 months’ old, GBS infection in babies is extremely rare.


Group B Strep is a recognised cause preterm delivery, maternal infections, stillbirths and late miscarriages. Babies born preterm are at particular risk of GBS infection as their immune systems are not as well developed as term babies.

Approximately one in every 1,750 babies born in the UK develops group B Strep infection. The underlying rate, without prevention efforts, would be around one in every 1,000 babies.

On average in the UK, at least

  • two babies a day develop a group B Strep infection 
  • one baby a week dies from their GBS infection, and
  • one baby a week survives with long-term disabilities – physical, mental or both.

For more information about the incidence of GBS bacteraemia (blood infection) in babies aged 0-90 days in England, Wales & Northern Ireland, click here.

*Image taken from Wikimedia Commons