Group A Streptococcal Infection

Causative agent

Group A streptococcus (GAS), Streptococcus pyogenes, are bacteria that can be found in the throat and on the skin. People may carry GAS without having any symptoms, while some may develop infections with various severity such as scarlet fever. The vast majority of GAS infections cause mild and common illnesses, such as sore throat (also known as strep throat) and skin infection like impetigo. On rare occasions, the bacteria can cause more severe and even life-threatening diseases.

GAS infections can occur at any time during the year. However, overseas data shows that strep throat and scarlet fever are more common in the winter and spring while impetigo is more common in the summer.

Invasive group A streptococcal (iGAS) disease

Life-threatening GAS disease may occur when bacteria get into parts of the body where bacteria usually are not found, such as blood, muscle or cerebrospinal fluid, causing iGAS disease such as necrotising fasciitis, streptococcal toxic shock syndrome (STSS) and meningitis. Although anyone can get iGAS disease, the elderly and young children, persons with chronic illnesses (e.g. diabetes) or persons who are immunocompromised may be at higher risk. People with breaks in the skin or with recent viral infections (e.g. chickenpox, influenza, etc.) are at higher risk of developing iGAS disease.

Clinical features

GAS infections usually cause mild illness with symptoms including sore throat, headache, fever and rash (scarlet fever), while symptoms of impetigo include red, itchy sores with yellow scabs.

For iGAS disease, other symptoms can appear depending on the part of body affected. Early signs and symptoms include high fever, chills, dizziness, nausea and vomiting, severe muscle aches and increasing pain, swelling and redness at site of wound. In case of STSS, serious symptoms can develop in a short time with low blood pressure, faster than normal heart rate, rapid breathing, and signs suggestive of organ failure.

Mode of transmission

GAS can be transmitted through respiratory droplets, touching skin sores of infected persons or through contact with contaminated environment or equipment.

Incubation period

The incubation period is variable for GAS infections. For example, the incubation period usually ranges from 1 to 3 days for scarlet fever, and 2 to 5 days for strep throat. For STSS, the incubation period varies depending on site of entry. Once initial symptoms occur, low blood pressure can develop within 24 to 48 hours.

Management

GAS infections can be treated with antibiotics. Seek medical advice promptly if symptoms of infection develop. In case of iGAS diseases, hospitalisation or surgery may be required.

Prevention

Members of the public should maintain good personal and environmental hygiene as well as practice good wound care. While there is no specific vaccine available against GAS, staying up to date with influenza, COVID-19 and chickenpox vaccines may also help as prevention of viral illnesses is likely to be important in reducing the risk of iGAS disease.

• Maintain good personal hygiene
  • Perform hand hygiene frequently especially before and after touching the mouth, nose or eyes; after touching public installations such as handrails or door knobs; or when hands are contaminated by respiratory secretion after coughing or sneezing.
  • Wash with liquid soap and water, and rub for at least 20 seconds. Then rinse with water and dry with either a clean cotton towel or a paper towel. If hand washing facilities are not available, or when hands are not visibly soiled, hand hygiene with 70 to 80% alcohol-based handrub is an effective alternative.
  • Cover your mouth and nose with tissue paper when coughing or sneezing. Dispose of soiled tissues into a lidded rubbish bin, then wash hands thoroughly.
  • Avoid sharing personal items e.g. eating utensils and towels.
• Maintain good environmental hygiene
  • Regularly clean and disinfect frequently touched surfaces such as furniture, toys and commonly shared items with 1:99 diluted household bleach (mixing 1 part of 5.25% bleach with 99 parts of water), leave for 15-30 minutes, and then rinse with water and keep dry. For metallic surface, disinfect with 70% alcohol.
  • Use absorbent disposable towels to wipe away obvious contaminants such as respiratory secretions, and then disinfect the surface and neighbouring areas with 1:49 diluted household bleach (mixing 1 part of 5.25% bleach with 49 parts of water), leave for 15-30 minutes and then rinse with water and keep dry. For metallic surface, disinfect with 70% alcohol.
  • Maintain good indoor ventilation.
• When having fever and other symptoms (e.g. increased redness, swelling and pain on wound), wear a surgical mask, refrain from work or attending classes at school, avoid going to crowded places, seek medical advice promptly and inform the doctor of any recent travel history
• Children suffering from scarlet fever should refrain from attending school or child care setting until fever has subsided and they have been treated with antibiotics for at least 24 hours
• Maintain proper wound management
  • Clean wounds immediately and cover properly with waterproof adhesive dressings until healed.
  • Prompt first aid care of even minor, non-infected wounds.
  • Perform hand hygiene before and after touching wounds.
  • Avoid going to swimming pools, other water facilities or natural bodies of water, e.g. rivers, lakes and oceans, if you have an open wound.
  • Consult doctor promptly if symptoms of infection develop, such as increasing redness, swelling and pain on the skin.