Invasive group A streptococcal infections: management of household contacts

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  • See also

    Cellulitis and other bacterial infections
    Parapneumonic effusion
    Sore Throat
    Bone and joint infection

    Key Points

    1. Invasive Group A Streptococcal disease (iGAS) is associated with significant morbidity and mortality
    2. There is an increased risk of secondary cases of iGAS in household contacts of an index case
    3. Inform household contacts about the clinical features of iGAS and provide chemoprophylaxis as soon as possible


    • Group A Streptococcus (GAS), also known as Streptococcus pyogenes, commonly colonises the skin, nasopharynx or anogenital tract of children
    • GAS causes a wide range of clinical disease in children, from mild illnesses such as pharyngitis and impetigo, to severe, life-threatening invasive infections 

    Invasive GAS disease (iGAS)

    iGAS is defined by the isolation of GAS from a normally sterile site. Manifestations include: 

    • bacteraemia/septicaemia
    • streptococcal toxic shock syndrome (STSS)
    • necrotising fasciitis
    • pneumonia and empyema
    • retropharyngeal abscess
    • osteomyelitis or septic arthritis
    • meningitis

    Cellulitis, scarlet fever and pharyngitis are not considered to be invasive disease

    Household contacts of a case of iGAS

    • Definition: those who have spent more than 24 hours in the same house as an index case in the 7 days prior to symptom onset until 24 hours after effective antibiotic therapy commenced
    • Household contacts are at increased risk of iGAS compared with the general population
    • Secondary cases usually occur within a month of the index case, but predominantly in the first 7 days


    • Some experts and guidelines recommend antibiotic chemoprophylaxis to reduce the risk of iGAS in household contacts, although this has not been studied extensively
    • Regardless of whether chemoprophylaxis is prescribed, all household contacts should be educated about their increased risk of iGAS and the early signs and symptoms of iGAS that require prompt medical evaluation. These include:
      • fever
      • severe muscle aches
      • sore throat
      • cellulitis
      • diarrhoea or vomiting
      • severe headache
    • Throat swabs to assess GAS carriage in asymptomatic close contacts are not helpful
    • Asymptomatic household contacts are not required to isolate or restrict activities

    Invasive GAS infections management of household contacts CPG draft final. Author: Amanda Wilkins

    Consider consultation with local paediatric (or infectious diseases specialist) team when

    Non-household close contacts or concerns regarding compliance with chemoprophylaxis

    Parent information

    Invasive Group A Streptococcal Disease

    Last updated May 2023

  • Reference List

    1. Carr J, Curtis N, Smeesters P, Steer A. Are household contacts of patients with invasive group A streptococcal disease at higher risk of secondary infection. Arch Dis Child. 2016. 101: 198-201.
    2. Department of Health, Australian Government. Invasive Group A Streptococcal (iGAS) Disease. 2021. (viewed 16 June 2022)
    3. Laho D, Blumental S, Botteaux A, Smeesters P. Invasive group A streptococcal infections: Benefit of clindamycin, intravenous immunoglobulins and secondary prophylaxis. Front Pediatr. 2021. 9:697938
    4. Lexicomp. Azithromycin and clindamycin monographs. (viewed 16 June 2022)
    5. Oliver J, Thielemans E, McMinn A et al. Invasive group A Streptococcus disease in Australian children: 2016 to 2018 – a descriptive cohort study. BMC Public Health. 2019. 19:1750.
    6. Perth Children’s Hospital, Children’s Antimicrobial Management Program. Medical Prophylaxis Guideline. 2021. (viewed 16 June 2022)