This article is from the Group B Strep FAQ, by firstname.lastname@example.org (Cheryl Sandberg) with numerous contributions by others.
Group B Streptococcus (GBS) is a type of bacteria that is found in the
lower intestine of 10-35% of all healthy adults and in the vagina and/or
lower intestine of 10-35% of all healthy, adult women. GBS should not be
confused with Group A Strep, which causes strep throat. A person whose body
carries GBS bacteria but who does not show signs of infections is said to
be "colonized" with GBS. GBS colonization is not contagious. GBS bacteria
are a normal part of the commonly found bacteria in the human body.
Normally, the presence of GBS does not cause problems. In certain
circumstances, however, GBS bacteria can invade the body and cause serious
infection: this is referred to as GBS disease.