Group B strep is a common type of bacteria. Another name for it is Streptococcus agalactiae. It's often carried in the intestines or lower genital tract.

It is usually harmless in healthy adults. But in newborns it can cause a serious illness known as group B strep disease.

Group B strep also can cause dangerous infections in adults with some long-term conditions, such as diabetes or liver disease. Older adults have a higher risk of illness from group B strep too.

If you're a healthy adult, there's nothing you need to do about group B strep.

If you're pregnant, get a group B strep screening test during your third trimester. If you have this type of bacteria in your body, medicines called antibiotics given to you during labor can protect your baby.

Infants

Most babies born to women carrying group B strep are healthy. But the few who are infected by group B strep during labor can become very ill. Some infections with this type of bacteria can be life-threatening.

In infants, illness caused by group B strep can start within six hours of birth. This is called early onset disease. Or the illness could start weeks or months after birth. This is called late onset disease.

Symptoms might include:

• Fever.
• Low body temperature.
• Trouble feeding.
• Sluggishness, limpness or weak muscle tone.
• Trouble breathing.
• Irritable behavior.
• Jittery movements.
• Seizures.
• Rash.
• Jaundice.

Adults

Many adults carry group B strep in their bodies and have no symptoms. Most often, the bacteria is carried in the bowel, vagina, rectum, bladder or throat.

But sometimes, group B strep can cause a urinary tract infection or other more-serious infections. Symptoms of infections that may be caused by group B strep include the following:

Urinary tract infection

• A strong, persistent urge to urinate.
• A burning sensation or pain when urinating.
• Passing frequent, small amounts of urine.
• Urine that appears red, bright pink or cola colored — a sign of blood in the urine.
• Pelvic pain.

Blood infection from the bacteria, also called bacteremia

• Fever.
• Chills.
• Confusion or lack of alertness.

Pneumonia

• Fever.
• Chills.
• Cough.
• Shortness of breath.
• Chest pain when you breathe or cough.

Skin or soft-tissue infection

• Swelling, warmth or a skin color change in the area of the infection.
• Pain in the area of the infection.
• Sores with pus or drainage.

Bone or joint infection

• Fever.
• Chills.
• Swelling, warmth or a change in skin color over the area of the infection.
• Pain in the area of the infection.
• Stiffness or no ability to use a limb or joint.

If you have symptoms of group B strep infection, call a member of your health care team right away. This is especially important if you have any of the following risk factors:

• You're pregnant.
• You have an ongoing medical condition.
• You're older than 65.

If you think your infant has symptoms of group B strep disease, call your baby's health care professional right away.

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 are not spread through sex, food or water. It isn't clear how the bacteria are spread to anyone other than newborns.

Group B strep can spread to a baby during a vaginal delivery. This happens if the baby is exposed to — or swallows — fluids that contains the bacteria.

Infants

An infant born prematurely, meaning earlier than 37 weeks, has a higher risk of getting group B strep disease.

A baby's risk also goes up if the pregnant parent has:

• Group B strep in the body.
• Breaking of the waters 18 hours or more before the baby is delivered.
• An infection of the placenta and amniotic fluid, called chorioamnionitis.
• A urinary tract infection during the pregnancy.
• A temperature higher than 100.4 F (38 C) during labor.
• Previously given birth to an infant with group B strep disease.

Adults

Adults age 65 and older have a higher risk of group B strep disease.

The risk is also higher for adults who have a condition that weakens the immune system or other serious diseases, such as:

• Diabetes.
• HIV.
• Liver disease.
• Heart disease.
• Cancer or a history of cancer.

Group B strep infection can lead to life-threatening disease in infants, including:

• Pneumonia.
• Inflammation of the membranes and fluid that surround the brain and spinal cord, called meningitis.
• Infection in the bloodstream, called bacteremia.

If you're pregnant, group B strep can cause the following:

• Urinary tract infection.
• Infection of the placenta and amniotic fluid, called chorioamnionitis.
• Infection of the membrane lining the uterus, called endometritis.
• Bacteremia.

If you're an older adult or you have a chronic health condition, group B strep bacteria can lead to any of the following conditions:

• Skin infection.
• Bacteremia.
• Urinary tract infection.
• Pneumonia.
• Bone and joint infections.
• Infection of the heart valves, called endocarditis.
• Meningitis.

If you're pregnant, the American College of Obstetricians and Gynecologists recommends a group B strep screening test during weeks 36 to 37 of pregnancy. Talk to your health care professional about when to get screened if you live outside of the U.S.

During the screening test, a member of your health care team takes swab samples from your vagina and rectum. Then the samples are sent to a lab for testing.

A "positive" test result means that you carry group B strep. It doesn't mean that you're ill or that your unborn baby will be affected. But you do have a higher risk of passing the bacteria to your baby.

Medicine can prevent group B bacteria from spreading to your baby during labor or delivery. An antibiotic through a needle in a vein, also called an IV, is given to you when labor begins. The antibiotic is usually penicillin or a related medicine.

If you're allergic to penicillin or related medicines, you might receive another antibiotic such as clindamycin or vancomycin instead. But it's not clear how well these other antibiotics work.

For that reason, your newborn's health care team closely watches the baby's health for up to 48 hours.

Taking antibiotics by mouth ahead of time won't help lower the risk of passing the bacteria to your baby. That's because the bacteria can return before labor begins.

Antibiotic treatment during labor also is recommended if you:

• Have a urinary tract infection.
• Delivered a previous baby with group B strep disease.
• Get a fever during labor.
• Haven't delivered your baby within 18 hours of your water breaking.
• Go into labor before 37 weeks and haven't been tested for group B strep.

Vaccine in development

Although it's not available yet, researchers are working on a group B strep vaccine. It could help prevent group B strep infections in the future.

If your newborn might have group B strep disease, a sample of your baby's blood or spinal fluid likely will be taken. A lab checks the sample for the bacteria that causes the infection.

If your baby appears ill, the baby might be given other tests, including:

• Urine culture.
• Lumbar puncture.
• Chest X-ray.

For adults who have an infection, a blood test can find out if group B strep is the cause. Learning the cause may be important for figuring out the right treatment.

Infants

If your baby tests positive for group B strep, the baby receives IV antibiotics through a vein. Depending on your baby's condition, the baby might need IV fluids, oxygen or other medicines.

Adults

Antibiotics can treat group B strep infection in adults. The choice of antibiotic depends on the location and extent of the infection. It also depends on your specific circumstances.

If you're pregnant and you have medical problems because of group B strep, you'll likely receive antibiotics by mouth. Most often, you'll be given penicillin, amoxicillin (Amoxil, Larotid) or cephalexin. All are considered safe to take during pregnancy.