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Group A Streptococcus

What is group A streptococcus?

Group A streptococcus is a bacteria. People commonly carry group A streptococcus in their throat or on their skin and have no symptoms of illness.  At times, group A streptococcus bacteria can cause mild illness such as strep throat or impetigo (minor skin infection).  On rare occasion, serious illness can occur when the group A streptococcus bacteria invade parts of the body such as the blood or tissue around the muscle (invasive disease).  Two of the more severe forms of invasive disease are necrotizing fasciitis (flesh eating bacteria) and Streptococcal Toxic Shock Syndrome (a rapidly progressive infection causing shock and multi-organ failure).

How are group A streptococci spread?

The bacteria spreads by direct contact with nose and throat mucus discharge from an infected individual or through direct contact with an infected wound on the skin.  Persons ill with group A streptococcus, such as those with strep throat or skin infections are most likely to spread infection.  Those who carry the bacteria but have no symptoms are much less contagious. People are not contagious after they have been treated with an appropriate antibiotic for 24 hours or longer, however, it is important to take all the prescribed antibiotics. Casual contact (as in work and school) and household items (like plates, cups, toys, etc.) rarely spread the bacteria.

Why does invasive group A streptococcal illness occur?

Invasive group A streptococcus illness occurs when the bacteria is able to invade parts of the body where it is not normally found (such as the blood or tissue around the muscle).  This rarely occurs, but may happen when a person has sores or other breaks in their skin that allow the bacteria to get into the body.  Health conditions that affect a person's immunity make it difficult to fight off infection and can make illness more likely. In addition, some strains of group A streptococcus are more likely to cause severe disease than others.  

Who is most at risk of invasive group A streptococcal disease? 

Most healthy people who come in contact with group A streptococcus may develop a throat or skin infection or have no symptoms at all.  People with chronic illnesses, such as cancer, heart disease, HIV, alcoholism and diabetes, those on kidney dialysis, and those who use medications such as steroids, are at higher risk for invasive disease.

Can invasive group A streptococcal disease be treated? 

Group A streptococcus bacteria can be treated with common antibiotics. In addition to antibiotics, care in an intensive care unit and sometimes surgery are necessary for severe illness.

What can be done to help prevent invasive group A streptococcal infections?

To reduce the spread of all types of group A streptococcal infections, a person can practice good handwashing, especially after coughing, sneezing and before preparing or eating foods. Persons with a sore throat should talk with their doctor. If tests are positive for strep throat, the ill person should stay home from work, school or daycare until antibiotics have been taken for at least 24 hours. All wounds should be kept clean and watched for signs of possible infection such as redness, swelling and pain in the wound area. If these signs occur, especially in a person who also has a fever, consult a doctor immediately.

Additional Resources:

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Boston Public Health Commission
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