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 and Streptococcal Toxic Shock Syndrome (STSS). Many otherwise healthy people can carry the bacteria and have no symptoms of disease.
What is invasive GAS disease?
Invasive GAS disease is a severe and sometimes life threatening disease that occurs when the bacteria reach parts of the body such as the blood, deep muscle and fat tissue, or lungs, where bacteria are not usually found. Two of the most severe, but least common, forms of invasive GAS disease are called “necrotizing fasciitis” (a destructive infection of muscle and fat tissue) and “STSS” (a rapidly progressing infection causing low blood pressure/shock and failure of such organs as the kidneys, liver, lungs, brain, etc.). Approximately 20-60% of patients with necrotizing fasciitis or STSS die. Only about 5-15% of patients with other forms of invasive GAS disease die.
How are GAS spread?
These bacteria are most commonly spread by direct contact with respiratory secretions (nose and throat discharges) or an infected individual or by contact with infected skin lesions. Communicability is probably 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 probably less contagious. In general, direct contact with infected secretions is needed to become infected. Household items like plates, cups, toys, etc. probably do not play a major role in disease transmission. There have been no reports of casual contacts, like co-workers or school classmates, developing invasive GAS disease following contact with a person who developed invasive GAS disease.
Who is most at risk of invasive GAS disease?
Few people who come in contact with a virulent strain of GAS will develop invasive GAS disease; most will have no symptoms or a mild infection. This may be because many people have been exposed to the same GAS strain in the past and have developed immunity in the form of protective proteins called “antibodies”, which halt the infection. Although healthy people can get invasive GAS disease, people with chronic illnesses like diabetes or chronic liver disease may be at higher risk. in addition, breaks in the skin, like cuts, surgical wounds, or chicken pox may provide an opportunity for the bacteria to enter the body.
What are the early symptoms of necrotizing fasciitis and STSS?
Early signs and symptoms of necrotizing fasciitis include fever, severe pain and swelling, and redness at the wound site. Early sings and symptoms of STSS include a generalized red rash, fever, dizziness, confusion, and abdominal pain.
How common is invasive GAS disease?
It is estimated that approximately 10,000-15,000 cases of invasive GAS disease occur in the United States each year resulting in roughly 2,000-3,000 deaths. The Centers for Disease and Prevention estimates there are between 500-700 cases of necrotizing fasciitis and 2,00-3,000 cases of STSS each year in the U.S.
Why does invasive GAS disease occur?
There are over 80 different strains of the group A streptococcus bacteria. A few of these (especially serotype M1 and M3) cause sever disease perhaps by producing substances that cause tissue destruction. These strains may also produce toxins causing shock (low blood pressure) or trigger other substances to be released that also cause shock.
Can invasive GAS disease be treated?
Group A streptococcus bacteria can be treated with common, inexpensive antibiotics. Penicillin is the drug of choice for both mild and severe disease (for penicillin-allergic patients, erythromycin can be used, although occasional resistance to erythromycin has been seen). Clindamycin may be added to the regimen in cases of necrotizing fasciitis. Certain other antibiotics are also effective. Rapid treatment is important to reduce the risk of death. In addition to antibiotics, supportive care in an intensive care unit and sometimes surgery are necessary. Unfortunately, even appropriate therapy does not prevent death in every case.
What can be done to help prevent invasive GAS infections?
The spread of all group A streptococcal infections may be reduced by good handwashing, especially after coughing and sneezing, after caring for persons with wounds or sore throats, before preparing food and before eating. Persons with strep throat should avoid work or school until they have been on antibiotic treatment for 24 hours. All wounds should be kept clean and bandaged. Wounds should be watched for possible signs of infection including increasing redness, swelling, and pain at the wound site.
This fact sheet is for informational purposes only. It should not be used for self-diagnosis or as a substitute for consultation with a health care provider. If you think that you may have this infection, or have questions about the disease described above, you should consult your health care provider.
For additional information on this disease, visit the Centers or Disease Control and Prevention website.
To contact the Epidemiology and Emerging Infections Program, please call 860-509-7994.