Diseases and surveillance

​​Invasive group A streptococcal (iGAS) disease​

Invasive group A streptococcal disease (iGAS) is a rare but serious bacterial infection. It progresses quickly and can be fatal. We monitor and report on iGAS. We provide guidelines to help minimise risk.

At a glance

About iGAS 

iGAS is caused by the Streptococcus pyogenes bacteria – also known as Group A Streptococcus.

These bacteria usually cause mild illnesses, like strep throat or impetigo (school sores). 

iGAS occurs when the bacteria enter internal parts of the body – such as the blood, muscles, soft tissues or fluid around the brain. When this happens, the infection can become life-threatening.

Read more about the infections caused by Streptococcus pyogenes.

Why it matters to public health

iGAS is a high public health priority.

It is rare but always serious and must be treated promptly. 

It can spread quickly in some settings, like aged care homes and other settings where people live in close quarters. Overcrowded housing and poor hygiene also make it easier for the bacteria to spread.

Because of these impacts, we:

Symptoms

If you’re looking for advice about your own health or treatment options, see healthdirect or speak with a qualified healthcare professional. Our role is to provide public health advice – information and guidance that helps prevent disease, protect communities and improve wellbeing at a population level.  

Streptococcus pyogenes infections usually cause mild illnesses including:

  • strep throat and tonsillitis
  • scarlet fever
  • skin infections – including cellulitis and impetigo (school sores).

A small number of people with Streptococcus pyogenes infections go on to develop iGAS. 

Common early symptoms of iGAS include:

Depending on the site of infection, iGAS can cause:

iGAS can become life threatening in less than 24 hours. It is fatal in up to 1 in 3 people.

People who recover from iGAS often have lifelong complications, including loss of limbs and severe scarring.

healthdirect’s symptom checker can help you decide whether to see a health professional.

Check your symptoms

Onset of symptoms

The start of iGAS symptoms depends on the site of infection. Symptoms can appear days to weeks after exposure to the bacteria.

How it spreads

Streptococcus pyogenes spreads from person to person, through:

  • respiratory droplets (coughing, sneezing)
  • contact with skin or infected wounds
  • kissing.

Many people carry the bacteria on their skin or in their throats without it making them sick. These people can spread the bacteria, but people with symptoms of infection or iGAS are more likely to pass it on to others.

People can be infected with Streptococcus pyogenes more than once.

Infectious period

People with iGAS are usually considered infectious from 7 days before symptoms appear until about 24 hours after starting antibiotics.

Prevention

There is no vaccine against iGAS or Streptococcus pyogenes infection.

Preventing Streptococcus pyogenes infection is the best way to protect against iGAS. This includes:

  • washing hands often, especially after coughing and sneezing
  • keeping any wounds clean and covered until healed
  • covering the mouth and nose when coughing and sneezing
  • cleaning bed linen, towels and frequently touched surfaces (such as doorknobs and taps) often.

People with Streptococcus pyogenes infections who are treated with antibiotics should stay home from childcare, school or work until 1 day after starting treatment.

Anyone who has been around someone with iGAS in the previous 30 days and develops a sore throat, skin sores or other symptoms should see a healthcare professional urgently.

Priority groups and settings

Some people are at greater risk of exposure to Streptococcus pyogenes and developing iGAS infection.

The risk of iGAS might be greater for some Aboriginal and Torres Strait Islander people. This is because of many factors, including barriers to culturally safe care. 

If you are at greater risk, it is especially important to take steps to protect yourself.

People at greater risk of severe disease

After being exposed to the bacteria, people are more likely to develop iGAS if they:

  • have recently given birth
  • are babies, especially newborns
  • have damaged skin, including open wounds, burns, surgical wounds or from injecting drug use
  • are aged 75 years or older
  • are immunocompromised
  • have certain chronic illnesses, especially diabetes or heart disease.

People at greater risk of exposure

Overcrowded housing and poor hygiene may increase the risk of iGAS spreading. 

People are more likely to be exposed if they: 

  • live with someone with iGAS
  • spend time in places where close contact is common, such as:
    • aged care homes
    • hospitals and healthcare facilities
    • early childhood education and care centres.
  • are experiencing homelessness
  • inject drugs.

Diagnosis and treatment

Depending on the site of infection, iGAS is diagnosed by testing:

  • blood
  • cerebrospinal fluid
  • fluid or tissue from an affected part of the body.

iGAS is a medical emergency. It can progress to life-threatening illness within 24 hours. People with iGAS need urgent medical attention.

You can use healthdirect’s directory to find a health service near you.

Find a health service

People with iGAS are usually treated in hospital with antibiotics.

Read more about how to manage or treat iGAS infections.

Surveillance and reporting

iGAS is a nationally notifiable disease – these are diseases that present a risk to public health.

Health authorities in each state and territory report cases to us daily through the National Notifiable Diseases Surveillance System (NNDSS).

These are part of our surveillance activities, which help us monitor case numbers around the country and understand disease patterns.

We analyse the data and report on case numbers and other data through our data visualisation tool, where you can filter and search the latest information.

Outbreaks

iGAS outbreaks happen more often in some groups and settings.

During outbreaks, public health units might:

  • trace and educate close contacts about Streptococcus pyogenes infections
  • offer antibiotics to newborns and their birthing parent, if Streptococcus pyogenes detected around the time of delivery
  • alert facilities such as aged care homes, schools and early childhood centres
  • notify healthcare professionals and issue public alerts
  • use specialised laboratory typing to confirm whether cases are linked.

Read more about how the Australian Government defines and plans for outbreaks.

Support

For information about iGAS infections in each state or territory, see:

If you need mental health support, see a list of organisations, websites and services that offer support, counselling and information.

Latest resources

Invasive Group A streptococcal disease – Surveillance case definition

This document contains the surveillance case definition for invasive Group A streptococcal disease (iGAS), which is nationally notifiable within Australia. State and territory health departments use this definition to decide whether to notify us of a case.

Invasive Group A Streptococcal (iGAS) Disease – CDNA National guidelines for Public Health Units

These guidelines outline Australia’s national minimum standard for surveillance, laboratory testing, case management and contact management for Invasive Group A Streptococcal (iGAS) disease.

Invasive Group A Streptococcal disease (iGAS) – Laboratory case definition

The Public Health Laboratory Network (PHLN) has developed standard case definitions for the diagnosis of key diseases in Australia. This document contains the laboratory case definition for iGAS disease.
Related resources
Last updated: