Group A Streptococcus

Group A Streptococcus and Streptococcal Toxic Shock Syndrome


Group A Streptococcus (Streptococcus pyogenes) is a bacterium commonly carried without symptoms in the throat and on the skin. This bacterium can cause a range of infections, from strep throat and skin infections to life-threatening invasive disease with sepsis. Two types of very serious invasive infections caused by this pathogen are necrotizing fasciitis (a dangerous soft-tissue infection that starts just below the skin and spreads along fascial planes, the flat layers of fibrous tissue that separate different layers of tissue), and streptococcal toxic shock syndrome (severe multi-organ system illness caused by toxin production).

Group A Streptococcus or GAS is spread by respiratory droplets and direct person-to-person contact. The bacteria are carried in discharges from the nose or throat, and on the skin, where they are often spread by unwashed hands. The bacteria are then deposited in the mouth, nose, or eyes of a new person. They can also enter the body through a cut or scrape. Anyone can become colonized or infected with GAS. However, people with long-term illnesses like cancer, diabetes, and kidney disease, and those who use medications such as steroids, are at higher risk for invasive disease. Breaks in the skin, like cuts, surgical wounds, or chickenpox blisters, can also provide an opportunity for streptococcal bacteria to enter the body.

Signs and symptoms depend on the site infected by GAS. Strep throat symptoms include fever, sore throat, and swollen lymph glands. Streptococcal skin infection causes red and painful skin (cellulitis), or sometimes weeping skin sores with a honey-colored crust (impetigo). Scarlet fever includes strep throat plus a characteristic "sandpapery" rash on the neck, chest, skin folds, and inner thighs. The rash can often be felt more easily than seen.

Early signs and symptoms of necrotizing fasciitis are fever and severe pain, swelling, heat, and redness at a wound site. Necrotizing fasciitis is known for the speed with which it attacks and destroys tissues under the skin, by dissecting along tissue planes.

Early signs and symptoms of streptococcal toxic shock syndrome (STSS) often include high fever, dizziness, and confusion, associated with low blood pressure and multiple organ system dysfunction. The bacteria may be recovered from a mucosal surface or blood. STSS is caused by toxin production and may or may not require invasive infection, although it is often associated with necrotizing fasciitis.


There is no vaccine for Group A Streptococcal infections. However, some infections may be preventable by maintaining good overall health, preventing skin breaks, keeping wounds clean, and washing hands thoroughly and often.

More about Group A Streptococcus:

Group A Streptococcal (GAS) Disease (CDC)

More about streptococcal toxic shock syndrome:

Streptococcal Toxic Shock Syndrome: All You Need to Know (CDC)

Page updated 12/21/2022