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Streptococcal Infections (Invasive Group A Strep)

What is Group A Streptococcus (Group A Strep)?
Group A streptococci are bacteria commonly found in the throat and on the skin. The vast majority of Group A Strep infections are 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 by the media as "the flesh-eating bacteria") and Streptococcal Toxic Shock Syndrome (STSS). In addition, people may carry Group A Strep in the throat or on the skin and have no symptoms of disease.
What is invasive Group A Streptococcal disease?
Invasive Group A Strep disease is a severe and sometimes life threatening infection in which the bacteria have invaded parts of the body where bacteria are not usually found, such as the blood, deep muscle and fat tissue, or the lungs. Two of the most severe, but less common, forms of invasive Group A Strep disease are called "necrotizing fasciitis" (a destructive 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 toxic shock syndrome die. Only about 10-15% of patients with other forms of invasive Group A Strep disease die.
How common is invasive Group A Streptococcal disease?
It is estimated that approximately 10,000-15,000 cases of invasive Group A Strep disease occur in the United States each year resulting in over 2,000 deaths. The Centers for Disease Control and Prevention estimates that there are between 500-1,500 cases of necrotizing fasciitis and 2,000-3,000 cases of STSS each year in the United States. In contrast, there are several million cases of strep throat and impetigo annually. Invasive Group A Strep was made a reportable disease in New York City in April, 1995. For data on Streptococcal infections in New York City visit EpiQuery.
How are Group A Streptococci spread?
These bacteria are spread by direct contact with respiratory secretions (nose and throat discharges) of an infected individual or by contact with infected skin lesions. The likelihood of spread increases 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.
Why does invasive Group A Streptococcal disease occur?
Invasive Group A Streptococcal infections occur when the bacteria gets 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 (e.g., diabetes, cancer). In addition, there are certain strains of Group A Strep that are more likely to cause severe disease than others. The reason why some strains 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 for invasive Group A Streptococcal disease?
Few people who come in contact with a virulent strain of Group A Strep will develop invasive Group A Strep disease; most will have a routine throat or skin infection and some may have no symptoms whatsoever. Although healthy people can get invasive Group A Strep disease, people with chronic illnesses like cancer, diabetes, and kidney failure, 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 the early signs and symptoms of necrotizing fasciitis and streptococcal toxic shock syndrome?
Early signs and symptoms of necrotizing fasciitis include fever, severe pain and swelling, and redness at the wound site. Early signs and symptoms of toxic shock syndrome may include fever, dizziness, confusion, rash and abdominal pain.
Can invasive Group A Streptococcal disease be treated?
Group A Streptococcal diseases can be treated with common, inexpensive antibiotics. Penicillin is the drug of choice for both mild and severe diseases. For penicillin-allergic patients with mild illness, erythromycin or clindamycin can be used, although occasional resistance has been seen. In addition to antibiotics, supportive care in an intensive care unit and sometimes surgery are necessary. Early treatment may reduce the risk of death although, unfortunately, even appropriate therapy doesn't prevent death in every case.
Should close contacts of individuals with invasive Group A Streptococcal disease be tested and treated?
There have been no reports of casual contacts, like co-workers or school classmates, developing invasive Group A Strep disease following contact with a person who developed invasive Group A Strep disease. Rarely, however, close contacts such as family members have developed invasive Group A Strep disease. Persons at highest risk include contacts with underlying diseases (e.g.,diabetes) or contacts of patients with the most severe forms of invasive Group A Strep (e.g., necrotizing fasciitis or fatal cases). Therefore, the decision regarding antibiotic prophylaxis should be made on an individual basis by the physicians involved.
What can be done to help prevent invasive Group A Streptococcal infections?
The spread of all types of Group A Streptococcal infections may be reduced by good handwashing, especially after coughing and sneezing, and before preparing foods and before eating. Persons with sore throats should be seen by a physician who can perform tests to find out whether or not it is strep throat; if so, one should stay home from work, school or day care until after 24 hours or more of taking an antibiotic. All wounds should be kept clean and watched for possible signs of infection, including increasing redness, swelling and pain at the wound site. If these signs occur, especially in a person who also has a fever, medical care should be sought. Currently, chickenpox is a common preceding illness among children with invasive Group A Streptococcal disease. This may be less common in the future since varicella (chickenpox) vaccine is now recommended routinely for all children.