- Group A streptococcus (GAS) is a type of bacteria often found in the throat and on the skin. It is also known as Type A streptococcal.
- Group A streptococcal bacteria can cause strep throat, scarlet fever, impetigo, cellulitis and other rarer but severe health conditions.
- Group A streptococcal disease can easily spread via respiratory droplets when coughing, sneezing or kissing and through direct skin contact.
- The best way to prevent group A streptococcal infections is to follow good hygiene practices and stay home when you’re sick.
- Group A streptococcal infections can spread quickly — see a doctor as soon as you notice symptoms. You may need treatment with antibiotics.
What is group A streptococcal infection?
Group A streptococcus, also known by the abbreviation GAS, is a type of bacteria often found in the throat and on the skin. Group A streptococcal infections commonly cause sore throats, also known as strep throat. This type of bacteria can be the cause of a rash sometimes known as scarlet fever and skin infections such as impetigo and cellulitis.
In rare cases the bacteria can also cause a severe, life-threatening infection known as invasive group A streptococcal disease (iGAS). Two of the most severe forms of iGAS are necrotising fasciitis (sometimes called ‘flesh-eating bacteria’) and streptococcal toxic shock syndrome.
Anyone can develop group A streptococcal disease, but people who are most at risk include:
- children under 5 years of age, especially infants
- older people over 65 years of age
- people with poor access to hygiene facilities
- people who live or spend time in crowded conditions
- people with weak immune systems or chronic illnesses
Children are more likely to become infected because they tend to be less aware of hygiene rules than adults. They also generally spend more time in crowded environments such as schools and play in close physical contact.
What are the symptoms of group A streptococcal infection?
The symptoms of group A streptococcal infection depend on where the infection develops in the body. Listed below are symptoms and signs of different types of group A streptococcal infection:
- Strep throat symptoms may include a sore throat and tonsils, pain when swallowing, fever, muscle aches and pains, and tiredness.
- Scarlet fever symptoms include a very red, sore throat, swollen glands and fever. Around 12 to 48 hours after infection, red blotches can appear on the skin, usually on the face, neck, underarms or groin. Red bumps can also form on the tongue, sometimes called a ‘strawberry tongue’.
- Impetigo causes sores on the skin that tend to form blisters. These blisters can burst and leave a moist area with a yellow brown crust at the edge.
- Cellulitis involves an area of skin becoming red and inflamed, painful and swollen, while the skin will often feel tight and warmer to the touch than the surrounding skin.
- Necrotising fasciitis is a serious skin infection that can cause deep, painful skin sores as well as fever, diarrhoea or vomiting, septic shock and organ failure.
Other diseases may develop following group A streptococcal infection. Listed below are some symptoms and signs of these complications :
- Rheumatic fever not only causes fever but often a sore throat that usually starts several weeks after the initial infection. People with rheumatic fever may feel tired, with muscle aches, joint pain and sometimes a skin rash as well.
- Post-streptococcal glomerulonephritis often causes ankle swelling and puffy eyes, blood in the urine and high blood pressure. It usually starts 10 to 14 days after the initial infection.
When should I see my doctor?
Visit your doctor if you have a sore throat or skin sores or a wound that seems to spread or is not getting better. If you think you or someone you care for has a group A streptococcal infection, it is important to see a doctor as soon as possible. The infection can spread through the body and can become serious if not promptly treated with antibiotics.
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What causes group A streptococcal infection?
Group A streptococcal infection is caused by bacteria that commonly exist on the skin and in the throat, including among many healthy people. Up to 1 in 3 people with group A streptococcal can carry the bacteria on their bodies without it causing any disease or without their experiencing any symptoms at all.
However, people who carry group A streptococcus can also spread the infection by coughing and sneezing droplets that contain the bacteria, or by direct skin contact. For example, if you are in close contact with someone with group A streptococcal bacteria, you may become infected if you:
- breathe in droplets from their cough or sneeze
- touch something with droplets on it and then touch your mouth or nose
- drink from their glass or eat with their cutlery
- touch their infected skin sores
- kiss them
How is group A streptococcal infection diagnosed?
Depending on your symptoms and the type of infection you have, your doctor will decide on which tests to perform to check whether you have a group A streptococcal infection.
If your doctor suspects you have strep throat, they may take a throat swab. Serious group A streptococcal disease (iGAS), including necrotising fasciitis and toxic shock syndrome will require blood tests and swabs of the infected areas.
How is a group A streptococcal infection treated?
Most common group A streptococcal infections are treated with prescription antibiotics. Your doctor will decide which antibiotic is best, depending on where your infection is located and how serious it is. Severe forms of the disease will usually need to be treated in hospital.
Can group A streptococcal infection be prevented?
The best way to prevent group A streptococcal infection is to maintain good hygiene. To decrease the spread of bacteria, wash your hands often, especially after sneezing or coughing and before preparing, serving or eating food.
Ensure surfaces such as bathroom sinks, taps and door handles, as well as clothes and bedlinen, are kept clean to protect all the members of your household.
If you or your child have ‘strep throat’ or another form of type A streptococcal infection, the infected person should stay home from pre-school, school or work for at least 24 hours after starting antibiotic treatment.
What are the complications of a group A streptococcal infection?
In rare cases, group A streptococcus can invade the body and cause severe and sometimes life-threatening infections. These infections are called invasive group A streptococcus (iGAS). People who develop iGAS disease will usually need to be treated in hospital.
People at increased risk of contracting this serious condition include older people, Indigenous Australians, people with chronic conditions, such as diabetes, and people who have a supressed immune system (for example, due to HIV or chemotherapy treatment).
A person with iGAS can become very sick within 12 to 24 hours, so it is important to seek medical care promptly. Early symptoms can include high fever, severe muscle aches and sometimes redness at the site of a skin wound. To find a health service in your area that’s open outside of regular hours, use the healthdirect Service Finder tool .
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Last reviewed: August 2021