Group A Streptococcus (GAS)
Group A Streptococcus is a bacterium often found in the throat and on the skin. People may carry group A streptococci in the throat or on the skin and have no symptoms of illness. Most GAS infections are relatively mild illnesses such as "strep throat," or impetigo. Occasionally these bacteria can cause severe and even life-threatening diseases.
Severe, sometimes life-threatening, GAS disease may occur when bacteria get into parts of the body where bacteria usually are not found, such as the blood, muscle, or the lungs. These infections are termed "invasive GAS disease." Two of the most severe, but least common, forms of invasive GAS disease are necrotizing fasciitis and streptococcal toxic shock syndrome. Necrotizing fasciitis (occasionally described by the media as "the flesh-eating bacteria") is a rapidly progressive disease which destroys muscles, fat, and skin tissue. Streptococcal toxic shock syndrome (STSS) results in a rapid drop in blood pressure and organs (e.g., kidney, liver, lungs) to fail. STSS is not the same as the "toxic shock syndrome" due to the bacteria Staphylococcus aureus which has been associated with tampon usage. While 10%-15% of patients with invasive group A streptococcal disease die from their infection, approximately 25% of patients with necrotizing fasciitis and more than 35% with STSS die.
How are group A streptococci spread?
These bacteria are spread through direct contact with mucus from the nose or throat of persons who are infected or through contact with infected wounds or sores on the skin. Ill persons, such as those who have strep throat or skin infections, are most likely to spread the infection. Persons who carry the bacteria but have no symptoms are much less contagious. Treating an infected person with an antibiotic for 24 hours or longer generally eliminates their ability to spread the bacteria. However, it is important to complete the entire course of antibiotics as prescribed. It is not likely that household items like plates, cups, or toys spread these bacteria.
What kind of illnesses are caused by group A streptococcal infection?
Infection with GAS can result in a range of symptoms:
- No illness
- Mild illness (strep throat or a skin infection such as impetigo)
- Severe illness (necrotizing faciitis, streptococcal toxic shock syndrome)
Severe, sometimes life-threatening, GAS disease may occur when bacteria get into parts of the body where bacteria usually are not found, such as the blood, muscle, or the lungs. These infections are termed "invasive GAS disease." Two of the most severe, but least common, forms of invasive GAS disease are necrotizing fasciitis and Streptococcal Toxic Shock Syndrome. Necrotizing fasciitis (occasionally described by the media as "the flesh-eating bacteria") destroys muscles, fat, and skin tissue. Streptococcal toxic shock syndrome (STSS), causes blood pressure to drop rapidly and organs (e.g., kidney, liver, lungs) to fail. STSS is not the same as the "toxic shock syndrome" frequently associated with tampon usage. About 20% of patients with necrotizing fasciitis and more than half with STSS die. About 10%-15% of patients with other forms of invasive group A streptococcal disease die.
How common is invasive group A streptococcal disease?
About 9,000-11,500 cases of invasive GAS disease occur each year in the United States, resulting in 1,000-1,800 deaths annually. STSS and necrotizing fasciitis each comprise an average of about 6%-7% of these invasive cases. In contrast, there are several million cases of strep throat and impetigo each year.
Why does invasive group A streptococcal disease occur?
Invasive GAS infections occur when the bacteria get past the defenses of the person who is infected. This may occur when a person has sores or other breaks in the skin that allow the bacteria to get into the tissue, or when the person’s ability to fight off the infection is decreased because of chronic illness or an illness that affects the immune system. Also, some virulent strains of GAS are more likely to cause severe disease than others.
Who is most at risk of getting invasive group A streptococcal disease?
Few people who come in contact with GAS will develop invasive GAS disease. Most people will have a throat or skin infection, and some may have no symptoms at all. Although healthy people can get invasive GAS disease, people with chronic illnesses like cancer, diabetes, and chronic heart or lung disease, and those who use medications such as steroids have a higher risk. Persons with skin lesions (such as cuts, chicken pox, surgical wounds), the elderly, and adults with a history of alcohol abuse or injection drug use also have a higher risk for disease.
Read more about GAS from the CDC.
Group B Strepococcus
Group B Streptococcus (group B strep) is a type of bacteria that causes illness in people of all ages. Also known as GBS or baby strep, group B strep disease in newborns most commonly causes sepsis (infection of the blood), pneumonia (infection in the lungs), and sometimes meningitis (infection of the fluid and lining around the brain). The most common problems caused by group B strep in adults are bloodstream infections, pneumonia, skin and soft-tissue infections, and bone and joint infections.
Early-Onset and Late-Onset GBS
- Early-onset disease — occurs during the first week of life.
- Late-onset disease — occurs from the first week through three months of life.
Early-onset disease used to be the most common type of disease in babies. Today, because of effective early-onset disease prevention, early and late-onset disease occur at similar low rates.
Group B Strep Can Cause these Illnesses in Babies
For early-onset disease, group B strep most commonly causes sepsis (infection of the blood), pneumonia (infection in the lungs), and sometimes meningitis (infection of the fluid and lining around the brain). Similar illnesses are associated with late-onset group B strep disease. Meningitis is more common with late-onset group B strep disease than with early-onset group B strep disease.
For both early and late-onset group B strep disease, and particularly for babies who had meningitis, there may be long-term consequences of the group B strep infection such as deafness and developmental disabilities. Care for sick babies has improved a lot and in the U.S., only 4-6% of babies with group B strep infections die.
On average, about 1,200 babies in the U.S. less than one week old get early-onset group B strep disease each year (see ABCs website for more surveillance information), with rates of group B strep disease higher among blacks. Group B strep can also cause some miscarriages, stillbirths and preterm deliveries. There are many different factors that lead to stillbirth, pre-term delivery, or miscarriage. Most of the time, the cause is not known.
Preventing Early-Onset GBS
There are 2 cornerstones to preventing newborn early-onset disease: testing all pregnant women for group B strep bacteria late in pregnancy, and giving antibiotics during labor to women who test positive for the bacteria.
1. Testing Pregnant Women
CDC’s guidelines recommend that a pregnant woman be tested, or screened, for group B strep in her vagina and rectum when she is 35 to 37 weeks pregnant. The test is simple and does not hurt. A sterile swab (“Q-tip”) is used to collect a sample from the vagina and the rectum. This is sent to a laboratory for testing.
About 25% of pregnant women carry group B strep in the rectum or vagina. Those women are considered group B strep positive. A woman may test positive at certain times and not at others. That’s why it’s important for all pregnant women to be tested for group B strep between 35 to 37 weeks of every pregnancy.
A woman who has the bacteria in her body usually does not feel sick or have any symptoms. However, she is at higher risk for passing group B strep to her baby during birth.
Women should talk to their doctor about their group B strep status.
2. Antibiotics During Labor
To help protect their babies from infection, pregnant women who test positive for group B strep in the current pregnancy should receive antibiotics (medicine) through the vein (IV) during labor. Also, pregnant women who have group B strep detected in their urine during the current pregnancy or who had a previous infant with group B strep disease should receive antibiotics during labor; they do not need to be screened at 35-37 weeks because they should receive antibiotics regardless of the screening result. Pregnant women who do not know whether or not they are group B strep positive when labor starts should be given antibiotics if they have:
- labor starting at less than 37 weeks (preterm labor);
- prolonged membrane rupture (water breaking 18 or more hours before delivery); or
- fever during labor.
Antibiotics help to kill some of the group B strep bacteria that are dangerous to the baby during birth. The antibiotics help during labor only — they can’t be taken before labor, because the bacteria can grow back quickly. Penicillin is the most common antibiotic that is given. For women who are severely allergic to penicillin, there are other antibiotics that can be given. Women should tell their doctor or nurse about any allergies during a checkup and try to make a plan for delivery. When women get to the hospital, they should remind their doctor if they are allergic to any medicines.
Penicillin is very safe and effective at preventing group B strep disease in newborns. There can be side effects from penicillin for the woman, including a mild reaction to penicillin (about a 10% chance). There is a rare chance (about 1 in 10,000) of the mother having a severe allergic reaction that requires emergency treatment.
Preventing Late-Onset Disease
Unfortunately, the method recommended to prevent early-onset disease (giving women who are group B strep positive antibiotics through the vein (IV) during labor) does not prevent late-onset disease. Although rates of early-onset disease have declined, rates of late-onset disease have remained fairly stable since 1990. At this time, a strategy has not yet been identified for preventing late-onset group B strep disease.
Alternative Prevention Strategies
There is no group B strep vaccine currently available to help mothers protect their newborns from group B strep disease. Researchers are working on developing a vaccine, which may become available one day in the future. Antibiotics taken by mouth instead of through the vein, and antibiotics taken before labor and delivery are not effective at preventing newborn group B strep disease. Birth canal washes with the disinfectant chlorhexidine do not reduce mother to baby transmission of group B strep bacteria or the risk of having a baby with early-onset disease. To date, receiving antibiotics through the vein during labor is the only proven strategy to protect a baby from early-onset group B strep disease.
Group B Strep Infections in Adults
While the rates of serious group B strep infections are much higher among newborns than among any other age group, serious group B strep infections occur in other age groups in both men and women.
The most common problems caused by group B strep in adults are:
- Bloodstream infections
- Pneumonia (infection in the lungs)
- Skin and soft-tissue infections
- Bone and joint infections
Rarely in adults, group B strep can cause meningitis (infection of the fluid and lining surrounding the brain).
Transmission and Prevention
The source of infection for adults is unknown. Since group B strep is a common organism in the gastrointestinal tract of men and women, this may be a source of some infection.
If doctors suspect an adult has an invasive group B strep infection, they will take a sample of sterile body fluids, such as blood or spinal fluid. Group B strep disease is diagnosed when the bacteria are grown in the laboratory from samples of those fluids. Samples take a few days to grow. Sometimes group B strep can cause mild disease in adults, such as urinary tract infections (UTIs, also called bladder infections), which also can be diagnosed in the lab with a sample of urine.
Group B strep infections are usually treated with penicillin or other common antibiotics. Sometimes soft tissue and bone infections may need surgery. Treatment will vary according to the kind of infection with group B strep someone has, and patients should ask their doctor about specific treatment options.
The rate of serious group B strep disease increases with age. The average age of cases in non-pregnant adults is about 60 years old. The rate of invasive disease is approximately 7 cases per 100,000 non-pregnant adults. The rate is highest among adults 65 years of age and older — 20-25 cases per 100,000. Most adult group B strep disease occurs in adults who have other medical conditions. These include: diabetes mellitus; cardiovascular disease; congestive heart failure; history of cancer; and obesity.
Serious group B strep infections in adults can be fatal. On average, 8% of adults with invasive group B strep infections (infections where the bacteria have entered a part of the body that is normally not exposed to bacteria) die. Risk of death is lower among younger adults, and adults who do not have other medical conditions.
Find out more about the different strep infections from the CDC at: http://www.cdc.gov/groupbstrep/index.html