Invasive Group A Streptococcal Disease (iGAS)

Key Messages:

  • Group A Streptococcal (GAS) disease is caused by infection with Group A streptococcus bacteria.
  • GAS bacteria generally spread person-to-person through:
    • droplet spread, such as when an infected person coughs or sneezes
    • through direct or indirect contact with the respiratory secretions or exudates from wounds from an infected person
    • direct or indirect contact of non-intact skin with infectious respiratory secretions or skin wound exudates
    • sharing of contaminated needles
  • Some people carry the bacteria without symptoms
  • Most GAS infections cause mild illnesses, such as streptococcal pharyngitis or impetigo, which are not reportable to public health
  • In rare cases, GAS becomes “invasive” (iGAS) when the bacteria enter the blood stream or deep tissue, which can be life-threatening
  • Suspected or confirmed cases of iGAS are reportable to local public health under the Health Protection and Promotion Act.
Introduction

Streptococcus pyogenes (S. pyogenes) are gram-positive cocci that grow in chains and are the most common species in group A of the Lancefield classification system. As a result, S. pyogenes is also known as ‘group A Streptococcus’ (GAS). The bacteria are a common colonizer in otherwise healthy people. Most GAS infections cause mild illnesses such as pharyngitis (“strep throat”) or impetigo. Invasive GAS (iGAS) infection occurs when bacteria enter normally sterile parts of the body such as blood, deep tissues, or meninges. Invasive infections can lead to more serious and potentially life-threatening conditions such as streptococcal toxic shock syndrome, sepsis, soft tissue necrosis or meningitis.  

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Local Epidemiology:

Although anyone can get an iGAS infection, some persons are at higher risk than others, due to age, other conditions or factors. Risk factors for iGAS include:

  • having wounds, cuts, or breaks in the skin, including from recent varicella (chicken pox) infection
  • Having chronic diseases, such as chronic lung or heart disease, diabetes, cancer
  • Living in crowded conditions
  • Having a weakened immune system, HIV infection
  • Substance use, including injection drugs
  • Being a close contact of someone with a recent GAS or iGAS infection
  • Recent surgery or being post-partum
  • Age: Children < 1 year of age and adults > 60 years of age

For more information on iGas in Ontario, please see Public Health Ontario’s Enhanced Epidemiologic Summary: Invasive Group A Streptococcal (iGAS) Disease in Ontario.

Further information on National level epidemiology can be found on the ‘Group A Streptococcal diseases: For health professionals’ page of the Government of Canada.

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Signs and symptoms

iGAS disease occurs when bacteria enter sterile parts of the body such as blood, deep tissues, or meninges. The most common clinical presentations of iGAS disease are skin or soft tissue infections, bacteremia with no septic focus, pneumonia, streptococcal toxic shock syndrome (STSS) and necrotizing fasciitis (‘flesh eating disease’).

Symptoms of iGAS vary depending on the site of infection and are often non-specific. Symptoms may include:

  • Fevers, chills, or influenza like symptoms
  • malaise
  • nausea, vomiting, diarrhea
  • joint pain, muscle aches
  • red, warm, painful, and rapidly spreading skin infection which may have pus or ulceration pain of unusual severity.

Initial symptoms in children may be difficult to distinguish from a viral infection and the signs and symptoms can be non-specific.

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Laboratory testing / Diagnosis

Testing Indications

Invasive GAS requires prompt and aggressive management as the disease is associated with significant morbidity and mortality. When possible and as clinically indicated, obtain a specimen from a normally sterile site for culture when there is clinical suspicion of iGAS disease.

Validated tests for diagnosis include standard culture with serogrouping for group A Streptococcus and nucleic acid amplification (NAAT) for Streptococcus pyogenes DNA.

Contact the testing laboratory for additional information about specimen types and turnaround time.

If testing for an outbreak, please contact Public Health Ontario laboratories and OPH prior to collecting samples. 

Isolates from invasive infections as well as outbreak specimens are forwarded to the Public Health Agency of Canada, Winnipeg for emm typing and emm Sub-Typing.

Reporting 

Results are reported to the ordering physician or health care provider as indicated on the requisition.

Cases that meet the case definition for iGAS are to be reported to the local public health unit as per the Health Protection and Promotion Act.

Case Definition – Confirmed Case of iGAS

  • Isolation of group A Streptococcus (Streptococcus pyogenes) or deoxyribonucleic acid (DNA) detection by nucleic acid amplification test (NAAT) from a normally sterile site (e.g., blood, cerebrospinal fluid, joint, pleural, pericardial fluid) with or without evidence of clinical severity,

OR

  • Isolation of Group A Streptococcus from a non-sterile site (e.g., skin) with evidence of severity*.

*For more information please see Appendix 1 of the Ontario Infectious Diseases Protocol - Disease: Group A Streptococcal Disease, invasive (iGAS), Ontario Ministry of Health.

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Reporting requirements

Suspected or confirmed cases of iGAS are reportable to local public health under the Health Protection and Promotion Act.

Monday to Friday from 8:30 am to 4:30 pm: Call 613-580-2424, extension 24224 and leave a detailed, confidential message including your contact information.

After hours, on weekends, or holidays: Call 3-1-1 and ask to speak to Public Health on call.

Non-invasive GAS infections are not reportable to OPH.

Please see the Reporting a communicable disease webpage for more information.

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Management

The mainstays of managing severe iGAS disease include fluid resuscitation, supportive treatment, and appropriate antibiotic therapy. When indicated, additional measures such as aggressive surgical debridement of any deep-seated infection may be necessary.

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Prevention

Transmission primarily occurs through respiratory droplet spread and direct contact with the nose or mouth secretions of an infected person but can also occur through wound secretions and sharing contaminated needles. Transmission through indirect contact with respiratory secretions can occur but is less common. Transmissibility from an infected person usually ends following 24 hours of appropriate antibiotic treatment. Therefore, for hospitalized cases, it is recommended that contact and droplet precautions be in effect until at least 24 hours after appropriate antimicrobial therapy has been initiated.

The prevention of illnesses that place individuals at risk of GAS infection is also important. This includes the prevention of respiratory infections (e.g., influenza) through available vaccines, reducing exposure to crowded settings when possible, practicing good respiratory and hand hygiene, self-isolation when ill, and using medical masks when appropriate.

Skin lesions can also serve as potential point of entry for GAS infection. Good wound management (i.e., wounds are properly cleansed, disinfected, and bandaged) can help reduce the risk of bacterial skin infection with GAS. People who use IV drugs are at higher risk of GAS skin infections and can be counselled on harm reduction strategies such as using clean equipment and not sharing equipment.

Prevention in close contacts

Certain strains of GAS are associated with severe invasive disease. Chemoprophylaxis is recommended for close contacts of severe cases of iGAS (as defined above). If prescribing chemoprophylaxis, OPH recommends that providers follow antibiotic regimens recommended in PHAC guidelines on the subject.

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Public health role

Public Health investigates reports of invasive GAS disease. Ottawa Public Health will identify and notify close contacts of an infected person and assess the need for preventive antibiotics. Close contacts of confirmed cases are advised to self-monitor for signs and symptoms of iGAS infection and/or fever for 30 days from diagnosis of the index case.

All cases of iGAS, whether confirmed or suspected, are reportable to local public health under the Health Protection and Promotion Act. 

If you have a suspected or confirmed case of iGAS disease, please reportit immediately to Ottawa Public Health by telephone:

  • Monday to Friday from 8:30 am to 4:30 pm: Call 613-580-2424, extension 24224
  • After hours, on weekends, or holidays: Call 3-1-1

     Please see the Reporting a communicable disease webpage for more information.

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Patient resources

Invasive Group A Streptococcal (iGAS) Disease, Ottawa Public Health

Group A streptococcal diseases (Streptococcus pyogenes) - Canada.ca, Government of Canada

About Group A Strep Infection, U.S. Centers for Disease Control and Prevention (CDC)

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Physician resources

General information:

Clinical guidelines:

Public health guidelines:

Laboratory testing:

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Contact us:

Monday to Friday from 8:30 am to 4:30 pm: Call 613-580-2424, extension 24224, select your language of choice by pressing 1 or 2 and then leave a detailed, confidential message including your contact information.

After hours, on weekends, or holidays: Call 3-1-1 and ask to speak to Public Health on call. To have your call prioritized as a health care professional, please identify yourself and your reason for calling; your call will be prioritized for answer.

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