Group B Streptococcus (GBS)

Group B Streptococcus (GBS), also known as Streptococcus agalactiae, is a type of bacteria commonly found in the digestive and urinary tracts of about a third of adults globally. GBS is usually harmless in healthy adults; however, it remains a major global health concern, especially for newborns and pregnant women.

In pregnancy, GBS can result in premature birth or stillbirth. Each year, GBS causes more than 500 000 premature births, and roughly 150 000 stillbirths and infant deaths globally. About 390 000 newborns also develop GBS disease, most of them born healthy and full-term. GBS in infants can cause life-threatening infections, such as sepsis, pneumonia, and meningitis. It is also one of the four main causes of acute bacterial meningitis in newborns globally.

GBS in adults, especially older individuals or those with weakened immune systems, can lead to bloodstream infections, pneumonia, skin infections, and, in rare cases, illnesses resembling toxic shock-syndrome.

The impact of GBS is most severe in low- and middle-income countries, where access to testing, antibiotics, and hospital care is often limited. Because GBS often causes no symptoms in pregnant women, it is difficult to detect without routine screening. A maternal GBS vaccine could save hundreds of thousands of babies each year by preventing preterm births, stillbirths, newborn deaths, and lifelong disabilities, making its development and equitable access a critical global health priority.

Not everyone who carries GBS will experience symptoms. GBS symptoms vary depending on the person's age and the part of the body where the infection occurs.

Group B Strep (GBS) infections in infants can occur at different times and may lead to serious illnesses. Early-onset GBS happens in the first week after birth. It can cause serious illnesses like blood infection (sepsis), lung infection (pneumonia), or brain infection (meningitis). Late-onset GBS happens from 7 to 89 days after birth. It can cause similar illnesses, especially meningitis, and usually starts more slowly.

Symptoms to watch for are:

• fever or feeling very cold
• trouble feeding
• very sleepy or hard to wake (lethargy)
• very fussy or hard to comfort
• breathing problems (fast or slow breathing)
• bluish or pale skin.

If parents see any of these signs in their baby, they need to get medical help right away.

GBS symptoms in adults also vary depending on where the infection occurs. Urinary tract infections can cause pain or burning during urination, frequent urination, pelvic pain, and blood in urine. Bacteraemia (a bloodstream infection) or sepsis symptoms can include fever, chills, confusion, and extreme tiredness and difficulty staying awake. Pneumonia symptoms include fever, chills, cough, shortness of breath, and chest pain. Skin and soft tissue infections, a common indication of GBS, can cause redness, swelling, and pain.

Currently, there are no approved vaccines or antibody treatments to prevent GBS infections.

WHO recommends universal testing of all pregnant women for GBS during an antenatal care visit. Women are usually tested with a simple vaginal or rectal swab between weeks 35 and 37. Pregnant women who test positive or have known risk factors should receive intravenous antibiotics (penicillin or ampicillin) at least four hours before delivery to help reduce the risk of transmitting GBS to their baby. Risk factors include a previous baby with GBS infection, GBS detected in the pregnant woman’s urine, or their water breaking more than 18 hours before delivery.

For those allergic to penicillin, alternatives like clindamycin or vancomycin may be used. This approach, of giving such drugs at least four hours before delivery, is intrapartum antibiotic prophylaxis (IAP) and reduces the risk of early-onset GBS infection in newborns by about 80%. However, IAP does not prevent late-onset infections, stillbirths, or preterm labour.

Infants with GBS infections should be treated with intravenous antibiotics, usually penicillin and gentamicin. The type of antibiotic and duration of treatment depends on the infant’s infection and lab results.

GBS vaccines designed to be given during pregnancy to protect infants are in the final stages of clinical testing. These vaccines have the potential to prevent both early- and late-onset GBS infections and could support global efforts to reduce premature births, stillbirths and infant mortality.