Invasive Group A Streptococcal Disease (iGAS) Fact Sheet

February 2024

Group A Streptococci (GAS) are bacteria that are often found in the nose, throat and/or on the skin of healthy people.

Toronto Public Health investigates reports of diseases of public health significance including invasive GAS (iGAS) disease by notifying close contacts of an infected person and assessing the need for preventive antibiotics.  Close contacts are advised to watch for symptoms of iGAS infection, including fever, for 30 days, and see their health care provider right away if they develop these symptoms.

These bacteria are spread through direct contact with secretions from the nose or throat of people who are infected (e.g., open mouth kissing, mouth to mouth resuscitation) or through contact with infected wounds or sores on the skin.

Those who are ill with GAS are the most likely to spread it to others.  People who carry the bacteria but have no symptoms are much less contagious.  Treating an infected person with an antibiotic for 24 hours or longer generally eliminates their ability to spread the bacteria.

Most people who get GAS will experience common infections such as sore (strep) throat, tonsillitis, and skin infections (e.g., impetigo, pyoderma). Less commonly a person may develop scarlet fever.

Occasionally, GAS causes “invasive” infections, which can be severe and possibly life threatening. This occurs when GAS infect sites that are usually sterile, such as blood, fluid surrounding the brain and spinal cord, or in the lining of muscles and joints.

Symptoms that may indicate iGAS include:

  • Streptococcal toxic shock syndrome – fever & chills, muscle aches, nausea & vomiting, a general feeling of being unwell, dizziness, confusion.
  • Meningitis – fever, headache, stiff neck, nausea, vomiting, light sensitivity, confusion.
  • Necrotizing fasciitis and myositis – swelling and/or redness of part of the skin that spreads quickly, severe pain, fever.

Close contacts of people with iGAS may be at increased risk of infection however, the risk of infection is low.

Close contacts include:

  • People living in the same household as the sick person.
  • People sharing sleeping arrangements with the sick person
  • People who have had direct contact with the sick person through mouth-to-mouth resuscitation, open mouth kissing, and open skin sores.
  • Injection drug users who shared needles with the sick person.

School classmates (kindergarten and older), work colleagues, as well as social or sports contacts of the sick person are not usually considered to be close contacts.

  • Clean your hands frequently by washing them with soap and water or using alcohol-based hand sanitizer
  • Cover your cough or sneeze with a tissue or into your upper sleeve
  • Ensure wounds and cuts are well cleansed and bandaged.
  • Stay up to date with immunizations. People with recent infections such as influenza and chickenpox may be at increased risk of invasive group A streptococcal disease (iGAS) infections.
  • Talk to your health care provider or Toronto Public Health at 416-338-7600.
  • Call 811 to connect to a registered nurse day or night for free, secure, and confidential health advice.