Causes

Many healthy people carry group B strep bacteria in their bodies. You might carry the bacteria in your body for a short time — it can come and go — or you might always have it. Group B strep bacteria aren't sexually transmitted, and they're not spread through food or water. How the bacteria are spread to anyone other than newborns isn't known.

Group B strep can spread to a baby during a vaginal delivery if the baby is exposed to — or swallows — fluids containing group B strep.