Streptococcal Infections

Streptococcal (strep-tuh-KAH-kul) infections are caused by various strains * of Streptococcus (strep-tuh-KAH-kus) bacteria.

What Are Streptococcal Infections?

Streptococci (STREP-tuh-KAH-kye) are common bacteria that live in the human body, including the nose, skin, and genital tract. These bacteria can destroy red blood cells, damage them, or cause no damage at all. The amount of damage they do is used to classify streptococcus strains. The ones that destroy red blood cells are known as beta-hemolytic (hemuh-LIH-tik) streptococci, and these strains are categorized as groups A through T.

Groups A and B streptococci are most often associated with disease. Group A strep (GAS) infections range from superficial skin infections and strep throat to serious and life-threatening illnesses such as toxic shock syndrome and necrotizing fasciitis (NEH-kro-tie-zing fash-eEYE-tis). Group B strep (GBS) is the leading cause of life-threatening infections in newborns. In pregnant women, GBS can lead to bladder * infections, infections of the uterus * , and death of the fetus * .

* ; and S. pneumoniae (nu-MO-nye), which can cause pneumonia * , middle ear infection, and meningitis * .

Group A Streptococcus (GAS) Infections

How common are GAS infections?

According to the National Institute of Allergy and Infectious Diseases (NIAID), more than 10 million cases of mild GAS infections, such as skin and throat infections, are diagnosed each year in the United States. Between 9,000 and 11,500 cases of more serious infections, including toxic shock syndrome and necrotizing fasciitis, occur annually. People with immune systems weakened by such diseases as diabetes * or cancer, are at a greater risk of developing serious GAS infections.

Are GAS infections contagious?

GAS bacteria are contagious. They spread through contact with fluid from the mouth or nose of an infected person or through contact with infected skin lesions * .

Examples of GAS infections
Shaking Hands with Semmelweis

Ignaz Philipp Semmelweis (1818–1865) was a Hungarian physician working at the Vienna (Austria) General Hospital in 1847, who suspected that doctors could spread disease by failing to wash their hands thoroughly after working with cadavers before delivering babies. At the time, up to 30 percent of women who gave birth in hospitals died of puerperal (pyoo-ER-puh-rul) fever, a group A strep bacterial infection that occurred after childbirth. Semmelweis noticed that women who delivered their babies with the help of midwives were less likely to become ill. He had his student doctors wash their hands with an antiseptic, which is a solution that prevents the growth of bacteria. Because the idea that germs could cause disease had not yet been introduced, Semmelweis’ ideas about hand washing were not well received until many years later.

Making the diagnosis

With skin infections, a doctor may take a sample from the affected area to culture * . For other types of suspected infections, blood samples are drawn and swabs of fluid from the patient's nose and throat are cultured for bacteria. A rapid strep test on a sample taken with a throat swab can also be done in a doctor's office.


Superficial skin infections often are treated with topical (on the skin) antibiotic ointments. Other GAS infections are treated with oral (by mouth), intramuscular (IM), or intravenous * (IV) antibiotics. Serious GAS infections require hospitalization, during which patients receive IV fluids and antibiotics. In some cases, such as with necrotizing fasciitis, surgical removal of damaged tissue is necessary. Treatment of rheumatic fever depends on the severity of the disease, but includes using antibiotics to treat strep infections, anti-inflammatory medicines like high-dose aspirin, and medications to treat heart complications.

What to expect

Symptoms of strep throat usually improve within one to two days after starting antibiotics. Skin infections often clear up within a week, but more serious infections can take weeks or even months to heal. Complications from serious bacterial infections include sepsis, shock, organ damage and failure, and death.


Maintaining good health and hygiene can help reduce the risk of bacterial infection. Not sharing food or eating utensils; washing hands frequently; and cleaning and bandaging cuts and scrapes can help prevent the spread of bacteria.

Group B Streptococcus (GBS) Infections

How common are GBS infections?

According to the Centers for Disease Control and Prevention, GBS is the most frequent cause of life-threatening infections in newborns. Early screening of pregnant women for GBS and treatment has reduced infection rates by approximately 70 percent since 2005. GBS infections are increasingly common in older adults, however, particularly in those over 65.

Are GBS infections contagious?

GBS infections are contagious and can pass from mother to child before or during birth. At least 25 percent of women are carriers of GBS at some point in their lives but do not become sick. The bacteria can be found in the bowel, vagina * , bladder, and throat.

Right elbow of a patient with group B streptococcus (GBS) bacteremia. The GBS bacteria have entered the blood stream and migrated to the tissues underneath the skin of the right elbow, causing localized swelling and redness.

Right elbow of a patient with group B streptococcus (GBS) bacteremia. The GBS bacteria have entered the blood stream and migrated to the tissues underneath the skin of the right elbow, causing localized swelling and redness.
CDC/Dr. Thomas Sellers.
Examples of GBS infections

Newborns can develop sepsis, pneumonia, and meningitis due to infection with GBS. Symptoms of GBS infection in newborns include fever, irritability, extreme sleepiness, breathing difficulties, and poor feeding.

GBS bacteria in pregnant women can cause urinary tract infections * as well as chorioamnionitis (KOR-e-o-am-nee-on-EYE-tis, infection of the womb and membranes surrounding the fetus) and stillbirth (a fetus that dies in the womb after 20 weeks of pregnancy). Symptoms of urinary tract infection include fever, pain, and a burning sensation during urination. Women with chorioamnionitis often do not show symptoms of infection until after childbirth. Symptoms include fever, belly pain, and rapid pulse.

The most common GBS infections in other people are urinary tract infections, sepsis, tissue infections, and pneumonia. GBS infections, including pneumonia and sepsis * , are more likely to be found in people with weakened immune systems or such chronic diseases as diabetes.

Making the diagnosis

GBS infections are diagnosed by performing cultures of blood, urine, or cerebrospinal fluid * to identify the bacteria.


GBS infections are treated with antibiotics, often given intravenously, and they usually require a hospital stay, particularly for newborns. Pregnant women with urinary tract infections usually are treated with antibiotics as well.

What to expect

Recovery from a GBS infection can take several weeks. Complications in infants, particularly those with meningitis, include hearing and vision loss and brain damage. Approximately 5 percent of cases of GBS disease in newborns are fatal.


Most cases in newborns can be prevented by testing women in the 35th to 37th week of pregnancy for the bacteria. A culture swabbed from the vagina and rectum * can determine whether a woman has GBS. If she does, giving IV antibiotics during labor reduces the risk of passing GBS to the baby. Vaccines * to prevent GBS infections during pregnancy were being developed in the early 2000s, but none are available as of 2016.

Alpha-Hemolytic Streptococcus Infections

How common are they?

Infections with alpha-hemolytic strep bacteria are common; many strains are found normally in humans.

Examples of alpha-hemolytic strep infections S. PNEUMONIAE (NU-MON-YI-EY) INFECTIONS S. VIRIDANS (VEER-IH-DANZ) INFECTIONS

Endocarditis is an infection of the inner surface of the heart or heart valves that can be caused by S. viridans and other bacteria. Bacteria can enter the bloodstream (during a dental procedure, for example) and attach to already damaged heart tissue or an abnormal heart valve, causing further damage. Symptoms include extreme tiredness, weakness, fever, chills, night sweats, and weight loss. The infection can progress and cause problems with heart function.

Making the diagnosis

Depending on the type of infection, a diagnosis is made by testing blood, sputum * , or cerebrospinal fluid samples for the presence of the bacteria.


Oral or IV antibiotics are used, depending on the severity of the infection. A hospital stay may be needed, particularly in cases of pneumonia or meningitis. Long courses of antibiotics, lasting several weeks or more, may be required to treat endocarditis.


Vaccines against S. pneumoniae are given routinely to infants and the elderly, as well as to children and adults with weakened immune systems or certain medical conditions. People with abnormal or damaged heart valves are given courses of antibiotics when they have some types of surgical procedures, including dental work, to prevent endocarditis from developing from the shedding of bacteria into the bloodstream that occurs with these procedures.

See also Bacterial Infections • Ear Infections (Otitis) • Endocarditis, Infectious • Fever • Impetigo • Meningitis • Pneumonia • Rheumatic Fever • Scarlet Fever • Sepsis • Skin and Soft Tissue Infections • Sore Throat/Strep Throat • Toxic Shock Syndrome • Urinary Tract Infections


Books and Articles

Playfair, John, and Gregory Bancroft. Infection and Immunity, 4th ed. Oxford, UK: Oxford University Press, 2013.

Roemmele, Jacqueline A., and Donna Batdorff. Surviving the Flesh-Eating Bacteria: Understanding, Preventing, Treating, and Living with the Aftermath of Necrotizing Fasciitis. Parker, CO: Outskirts Press, 2015.


MedlinePlus. “Streptococcal Infections.” U.S. National Library of Medicine, National Institutes of Health. (accessed July 12, 2016).

PubMed Health. “Strep Throat.” U.S. National Library of Medicine. (accessed July 12, 2016).


Centers for Disease Control and Prevention. 1600 Clifton Rd., Atlanta, GA 30329-4027. Toll-free: 800-232-4636. Website: (accessed July 12, 2016).

Infectious Diseases Society of America. 1300 Wilson Blvd., Suite 300, Arlington, VA 22209. Telephone: 703-299-0200. Website: (accessed July 12, 2016).

National Institute of Allergies and Infectious Diseases. Office of Communications and Government Relations, 5601 Fishers Ln., MSC 9806, Bethesda, MD 20892-9806. Telephone: 301-496-5717. Website: (accessed July 12, 2016).

* strains are various subtypes of organisms, such as viruses or bacteria.

* bladder (BLAD-er) is the hollow organ that stores urine produced by the kidneys prior to discharge from the body

* uterus (YOO-teh-rus) is the muscular pear-shaped internal organ in a woman where a baby develops until birth.

* fetus (FEE-tus) is the term for an unborn human after it is an embryo, from nine weeks after fertilization until childbirth.

* endocarditis (en-do-kar-DYE-tis) is an inflammation of the valves and internal lining of the heart, known as the endocardium (ENdoh-KAR-dee-um). Endocarditis is usually caused by an infection.

* pneumonia (nu-MO-nyah) is inflammation of the lungs.

* meningitis (meh-nin-JY-tis) is an inflammation of the meninges, the membranes that cover and protect the brain and the spinal cord. Meningitis is most often caused by infection with a virus or a bacterium.

* diabetes (dye-uh-BEE-teez) is a condition in which the body's pancreas does not produce enough insulin or the body cannot use the insulin it makes effectively, resulting in increased levels of sugar in the blood.

* lesion (LEE-zhun) is a general term referring to a sore or a damaged or irregular area of tissue.

* tonsils are paired clusters of lymphatic tissue in the throat that protect the body from bacteria and viruses that enter through a person's nose or mouth.

* lymph nodes (LIMF) are small bean-shaped masses of tissue containing immune system cells that fight harmful microorganisms. Lymph nodes may swell during infections.

* shock is a serious condition in which blood pressure is very low, and not enough blood flows to the body's organs and tissues. Untreated shock may result in death.

* arthritis (ar-THRY-tis) refers to any of several disorders characterized by inflammation of the joints.

* inflammation (in-fla-MAY-shun) is the body's reaction to irritation, infection, or injury, and involves swelling, pain, redness, and warmth.

* culture (KUL-chur) is a test in which a sample of fluid or tissue from the body is placed in a dish containing material that supports the growth of certain organisms. Typically, within days the organisms will grow and can be identified.

* intravenous (in-tra-VEE-nus), or IV, means within or through a vein. For example, medi-cations, fluid, or other substances can be given through a needle or soft tube inserted through the skin's surface directly into a vein.

* vagina (vah-JY-nah) is the canal, or passageway, in a woman that leads from the uterus to the outside of the body.

* urinary tract infection (YOORih-nair-e), or UTI, is an infection that occurs in any part of the urinary tract. The urinary tract is made up of the urethra, bladder, ureters, and kidneys.

* sepsis is a potentially serious spreading of infection, usually bacterial, through the bloodstream and body.

* cerebrospinal fluid (seh-ree-bro-SPY-nuhl) is the fluid that surrounds the brain and spinal cord.

* rectum is the final portion of the large intestine, connecting the colon to the outside opening of the anus

* vaccines (vak-SEENS) are preparations of killed or weakened germs, or a part of a germ or product it produces, given to prevent or lessen the severity of the disease that can result if a person is exposed to the germ itself.

* sinuses (SY-nuh-ses) are hollow, air-filled cavities in the facial bones.

* sputum (SPYOO-tum) is a substance that contains mucus and other matter coughed up from the lungs, bronchi, and trachea.

  This information is not a tool for self-diagnosis or a substitute for professional care.