Invasive group A streptococcal disease (iGAS)

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Invasive group A streptococcal disease (iGAS) is a serious infection that occurs when bacteria called group A beta-hemolytic streptococci (GAS) spread to different organs in the body.

Key points

  • A typical GAS infection causes common childhood illnesses, such as strep throat, scarlet fever or impetigo, that can be treated at home with oral antibiotics.
  • In rare cases, GAS bacteria may invade and infect other organs, such as the bloodstream, muscles, bones, joints, lungs and the brain. Children with invasive disease can experience severe skin and muscle infection and damage (necrotizing fasciitis).
  • The bacteria produce toxins that can have life-threatening effects and require treatment with intravenous antibiotics and other medications to minimize damage to vital organs.
  • It is not known why some healthy children with no risk factors get more severe GAS infections than others.

Who is at risk of getting an iGAS infection?

Group A streptococcal (GAS) infections most commonly cause strep throat in school-age children. It can also cause scarlet fever or skin infections. These are easily treated with antibiotics at home. In rare cases, some strains of the same bacteria can cause severe disease by producing toxins and invading other organs. Invasive GAS disease can occur in people who are at higher risk. This includes infants, children and senior adults, anyone with a weak immune system, and anyone with a recent respiratory virus, influenza or varicella (chicken pox) infection. However, there has been an unexplained increase in the number of healthy children with no previous risk factors who have been diagnosed with iGAS infections.

My child was diagnosed with strep throat. Will they get iGAS?

Children with strep throat do not appear to be at higher risk of developing iGAS. While it is the same bacteria that causes strep throat and iGAS, there are many different strains, or sub-types, of group A Streptococcus. Only certain strains cause invasive disease, and they may be different from the ones that cause common strep infections.

How do I know if my child has iGAS?

Children with iGAS have a fever and are ill. Trust your instincts. Parents or caregivers should seek urgent medical care if their child has:

  • change in behaviour: Behaviour changes include being less alert, being confused or drowsy, not responding as usual, or having unusual movements or unusual speech.
  • change in breathing: Breathing changes include fast breathing, difficulty speaking and breathlessness.
  • dehydration: If your child is not drinking enough, has frequent vomiting or diarrhea, appears weak or is urinating less than every 8 hours.
  • change in skin tone or colour: Children with cold clammy skin, blue lips, gray skin colour or purple blotches.
  • a rapidly spreading rash with or without severe pain or swelling: This can be a sign of iGAS infection in skin and muscle.
  • rapid progression of their symptoms even if they were recently assessed by a health-care provider and even if they were already started on an oral antibiotic.
  • fever that has lasted for 5 days: Children with persistent fevers should be assessed by a health-care provider during their illness, whereas children with weakened immune systems or infants under 3 months of age should be seen at the onset of fever.

Symptoms include:

  • fever
  • change in behaviour
  • irritability or confusion
  • thirst, dry mouth, reduced urination
  • faster breathing
  • change in skin colour
  • rapidly spreading rash
  • severe pains in the arms, legs, neck or back
  • rapid progression of symptoms

How can I protect my child?

If your child has been exposed to someone with a strep infection and develops similar symptoms (skin infection, sore throat, rash or fever), take them to their regular health-care provider to get a throat swab. Inform their health-care provider they have been exposed to someone with strep. If diagnosed with a strep infection, make sure your child stays home for the first 24 hours after starting antibiotics to reduce transmission to others and completes the prescribed course of antibiotic.

Ensure that your child’s vaccinations are up to date against all preventable infections, including varicella (chicken pox) and influenza.

Practice regular hand washing to reduce the spread of respiratory viral infections that might precede iGAS.

My child has been diagnosed with iGAS. Is the rest of my family safe?

Your local public health unit will investigate any child diagnosed with iGAS and provide counselling regarding the risk of exposure to household members. In some cases, the public health practitioner will recommend prophylaxis (preventative) oral antibiotics for people who had close contact with the ill child to reduce the risk of infection from exposure to the bacteria.

Last updated: February 1st 2024