Group A Streptococcal Infections

Last Editorial Review: 11/16/2007
  • Scarlet fever
  • Severe strep infections
  • Research
  • Overview of streptococcal infections

    Group A streptococcal (strep) infections are caused by group A streptococcus, a bacterium responsible for a variety of health problems. These infections can range from a mild skin infection or sore throat to severe, life-threatening conditions such as toxic shock syndrome and necrotizing fasciitis, commonly known as flesh eating disease. Most people are familiar with strep throat, which along with minor skin infection, is the most common form of the disease. Health experts estimate that more than 10 million mild infections (throat and skin) like these occur every year.

    In addition to step throat and superficial skin infections, group A strep bacteria can cause infections in tissues (group of cells joined together to perform the same function) at specific body sites, including lungs, bones, spinal cord, and abdomen.

    Strep throat

    Symptoms of strep throat

    Your health care provider may call it acute streptococcal pharyngitis. If you have strep throat infection , you will have a red and painful sore throat and may have white patches on your tonsils. You also may have swollen lymph nodes in your neck, run a fever, and have a headache. Nausea, vomiting, and abdominal pain can occur but are more common in children than in adults.

    Transmission of strep throat

    You can get strep throat and other group A strep infections by direct contact with saliva or nasal discharge from an infected person. Most people do not get group A strep infections from casual contact with others, but a crowded environment like a dormitory, school, or an institutional setting such as a nursing home can make it easier for the bacteria to spread. There have also been reports of contaminated food, especially milk and milk products, causing infection. You can get sick within 3 days after being exposed to the germ. Once infected, you can pass the infection to others for up to 2 to 3 weeks even if you don't have symptoms. After 24 hours of antibiotic treatment, you will no longer spread the germs to others.

    Diagnosis of strep throat

    Your health care provider will take a throat swab. This will be used for a culture (a type of laboratory test) or a rapid strep test, which only takes 10 to 20 minutes. If the result of the rapid test is negative, you may get a follow-up culture to confirm the results, which takes 24 to 48 hours. If the culture test is also negative, your health care provider may suspect you do not have strep, but rather another type of infection. The results of these throat cultures will affect what your health care provider decides to be the best treatment. Most sore throats are caused by viral infections, however, and antibiotics are useless against them.

    Treatment for strep throat

    If you have a strep infection, your health care provider will prescribe an antibiotic. This will help reduce symptoms, and after 24 hours of taking the medicine, you will no longer be able to spread the infection to others. Treatment will also reduce the chance of complications.

    Health experts think penicillin is the best medicine for treating strep throat because it has been proven to be effective, safe, and inexpensive. Your health care provider may have you take pills for 10 days or give you a shot. If you are allergic to penicillin there are other antibiotics your health care provider can give you to clear up the illness.

    During treatment, you may start to feel better within 4 days. This can happen even without treatment. Still, it is very important to finish all your medicine to prevent complications.

    Children with strep throat are usually treated with amoxicillin.

    Complications of strep throat

    Untreated group A strep infection can result in rheumatic fever and post-streptococcal glomerulonephritis (PSGN). Rheumatic fever develops about 18 days after a bout of strep throat and causes joint pain and heart disease. It can be followed months later by Sydenham's chorea, a disorder where the muscles of the torso and arms and legs are marked with dancing and jerky movements. PSGN is an inflammation of the kidneys that may follow an untreated strep throat but more often comes after a strep skin infection. Both disorders are rarely seen in the United States because of prompt and effective treatment of most cases of strep throat.

    Skin infections: Impetigo, Cellulitis, Erysipelas


    Impetigo is an infection of the top layers of the skin and is most common among children ages 2 to 6 years. It usually starts when the bacteria get into a cut, scratch, or insect bite. Impetigo is usually caused by staphylococcus (staph), a different bacterium, but can be caused by group A streptococcus. Skin infections are usually caused by different types (strains) of strep bacteria than those that cause strep throat. Therefore, the types of strep germs that cause impetigo are usually different from those that cause strep throat.

    Symptoms of impetigo

    Symptoms start with red or pimple-like lesions (sores) surrounded by reddened skin. These lesions can be anywhere on your body, but mostly on your face, arms, and legs. Lesions fill with pus, then break open after a few days and form a thick crust. Itching is common. Your health care provider can diagnose the infection by looking at the skin lesions.

    Transmission of impetigo

    The infection is spread by direct contact with wounds or sores or nasal discharge from an infected person. Scratching may spread the lesions. From the time of infection until you show symptoms is usually 1 to 3 days. If your skin doesn't have breaks in it, you can't be infected by dried streptococci in the air.

    Treatment for impetigo

    Your health care provider will prescribe oral antibiotics, as with strep throat. This treatment may also include an antibiotic ointment to be used on your skin.

    Cellulitis and erysipelas

    Cellulitis is inflammation of the skin and deep underlying tissues. Erysipelas is an inflammatory disease of the upper layers of the skin. Group A strep germs are the most common cause of both conditions.

    Symptoms of cellulitis and erysipelas

    Symptoms of cellulitis may include fever and chills and swollen "glands" or lymph nodes. Your skin will be painful, red, and tender. Your skin may blister and then scab over. You may also have perianal (around the anus) cellulitis may with itching and painful bowel movements.

    With erysipelas, a fiery red rash with raised borders may occur on your face, arms, or legs. Your skin will be hot, red, and have sharply defined raised areas. The infection may come back, causing chronic swelling of your arms or legs (lymphedema).

    Transmission of cellulitis or erysipelas

    Both cellulitis and erysipelas begin with a minor incident, such as a bruise. They can also begin at the site of a burn, surgical cut, or wound, and usually affect your arm or leg. When the rash appears on your trunk, arms, or legs, however, it is usually at the site of a surgical cut or wound. Even if you have no symptoms, you carry the germs on your skin or in your nasal passages and can transmit the disease to others.

    Diagnosis and treatment of cellulitis and erysipelas

    Your health care provider may take a sample or culture from your skin lesions to identify the bacteria causing infection. He or she may also recover the bacteria from your blood. Depending on how severe the infection is, treatment involves either oral or intravenous (through the vein) antibiotics.


    Sore Throat or Strep Throat? How to Tell the Difference See Slideshow

    Scarlet Fever

    Scarlet fever is another form of group A strep disease that can follow strep throat. It is usually contagious and lasts for a specific length of time whether or not it is treated.

    Symptoms of scarlet fever

    In addition to the symptoms of strep throat, a red rash appears on the sides of your chest and abdomen. It may spread to cover most of your body. This rash appears as tiny, red pinpoints and has a rough texture like sandpaper. When pressed on, the rash loses color or turns white. There may also be dark red lines in the folds of skin. You may get a bright strawberry-red tongue and flushed (rosy) face, while the area around your mouth remains pale. The skin on the tips of your fingers and toes often peels after you get better. If you have a severe case, you may have a high fever, nausea, and vomiting.

    Transmission of scarlet fever

    You can get scarlet fever the same way as strep throat-through direct contact with throat mucus, nasal discharge, and saliva of an infected person.

    Treatment for scarlet fever

    Like strep throat, your health care provider will treat scarlet fever with antibiotics.

    Severe strep infections

    Some types of group A strep bacteria cause severe infections. These include

    In 2004, 3,833 cases of severe group A streptococcal disease were reported to the Centers for Disease Control and Prevention.

    All severe group A strep infections may lead to shock, organ failure, and death. Health care providers must recognize and treat such infections quickly.

    Health care providers diagnose these infections by looking at blood counts and doing urine tests as well as cultures of blood or fluid from a wound site.

    Antibiotics used to treat these severe infections include penicillin, erythromycin, and clindamycin. If you have severe tissue damage, your health care provider may need to remove the tissue surgically or amputate the limb.

    People at the greatest risk of getting a severe strep infection are

    • Children with chickenpox
    • People with suppressed immune systems
    • Burn victims
    • Elderly people with cellulitis, diabetes, blood vessel disease, or cancer
    • People taking steroid treatments or chemotherapy
    • Intravenous drug users

    Severe group A strep disease may also occur in healthy people who have no known risk factors.


    Through research, health experts have learned that there are more than 120 different strains of group A streptococci, each producing its own unique proteins. Some of these proteins are responsible for specific group A streptococcal diseases.

    With the support of the National Institute of Allergy and Infectious Diseases (NIAID), scientists have determined the genetic sequence, or DNA code, for five different strains of the group A streptococcus organism.

    By studying an organism's genes, scientists learn which proteins are responsible for virulence, crucial information that will lead to new and improved drugs and vaccines. NIAID funds are supporting research for developing a group A streptococcus vaccine and several candidate vaccines are in various phases of development.

    As a result of NIAID-supported research, the first group A streptococci vaccine clinical trial in 30 years was conducted. The vaccine was well tolerated by patients and has led to further clinical evaluation of a similar vaccine candidate. An effective vaccine will prevent not only strep throat and impetigo but also more serious invasive disease and post-infectious complications like rheumatic fever. In addition, vaccine development efforts include NIAID support of epidemiological studies to determine the burden of group A streptococcal disease and characterize group A streptococcal strains causing illness in the United States and developing countries.


    Just about any painful sore throat is caused by strep. See Answer

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    National Institutes of Health, National Institute of Allergy and Infectious Diseases