Group A Strep: Questions and Answers
What is Group A streptococcus (GAS)?
Group A streptococci are bacteria commonly found in the throat and on the skin. The vast majority of GAS infections are relatively mild illnesses, such as strep throat and impetigo. Occasionally, however, these bacteria can cause much more severe and even life-threatening diseases such as necrotizing fasciitis (occasionally described as "the flesh-eating bacteria") and streptococcal toxic shock syndrome (STSS). In addition, people may carry Group A streptococci in the throat or on the skin and have no symptoms of disease.
How are Group A streptococci spread?
These bacteria are spread by direct contact with nose and throat discharges of an infected individual or with infected skin lesions. The risk of spread is greatest when an individual is ill, such as when people have strep throat or an infected wound. Individuals who carry the bacteria but have no symptoms are much less contagious. Treatment of an infected person with an appropriate antibiotic for 24 hours or longer eliminates contagiousness. However, it is important to complete the entire course of antibiotics as prescribed. Household items like plates, cups, toys, etc., do not play a major role in disease transmission.
What is invasive Group A streptococcal disease?
Invasive GAS disease is a severe and sometimes life-threatening infection in which the bacteria have invaded parts of the body, such as the blood, deep muscle and fat tissue or the lungs. Two of the most severe, but least common, forms of invasive GAS disease are called "necrotizing fasciitis" (infection of muscle and fat tissue) and "streptococcal toxic shock syndrome" (a rapidly progressing infection causing low blood pressure/shock and injury to organs such as the kidneys, liver and lungs). Approximately 20% of patients with necrotizing fasciitis and 60% with STSS die. Only about 10% to 15% of patients with other forms of invasive Group A streptococcal disease die.
How common is invasive Group A streptococcal disease?
Approximately 10,000-15,000 cases of invasive GAS disease occur in the United States each year, resulting in more than 2,000 deaths. The Centers for Disease Control and Prevention estimates there are between 500 and 1,500 cases of necrotizing fasciitis and 2,000 to 3,000 cases of STSS each year in the United States. In contrast, there are several million cases of strep throat and impetigo annually. Clusters of cases or outbreaks of invasive GAS have not been reported in any schools or communities in New York State.
Why does invasive Group A streptococcal disease occur?
Invasive Group A streptococcal 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. Health conditions that decrease a person’s immunity to infection also make invasive disease more likely. In addition, there are certain strains of GAS that are more likely to cause severe disease than others. The reason why some strains will cause more severe illness is not totally clear but may involve the production of substances (toxins) that cause shock and organ damage, and enzymes that cause tissue destruction.
Who is most at risk of invasive Group A streptococcal disease?
Few people who come in contact with a virulent strain of GAS will develop invasive GAS disease; most will have a routine throat or skin infection and some may have no symptoms whatsoever. Although healthy people can get invasive GAS disease, people with chronic illnesses like cancer, diabetes and kidney dialysis, and those who use medications such as steroids are at higher risk. In addition, breaks in the skin, like cuts, surgical wounds or chickenpox may provide an opportunity for the bacteria to enter the body.
What are infection control measures?
The risk of spread of invasive and non-invasive GAS can be minimized by thorough hand washing after coughing, sneezing, and before/after providing patient care. Persons with a sore throat should be seen by a doctor who can perform tests to determine if the infection is due to strep. Cuts or wounds should be kept clean and watched for signs of infection, which include pus, redness, swelling, and pain at the wound site. Early signs of streptococcal toxic shock may include fever, rash, dizziness, and abdominal pain. If these signs occur, medical care should be promptly sought.
Source: Bureau of Communicable Disease Control, New York State Department of Health, Albany.
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