Group A streptococcal diseases (Streptococcus pyogenes)

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About Group A streptococcal diseases

Streptococcus pyogenes, also called group A streptococcus (GAS) is a common bacterium that can cause many types of GAS diseases. Most illnesses are mild or moderate, and may include:

  • strep throat (pharyngitis)
  • skin or wound infections (including impetigo and cellulitis)
  • scarlet fever

In rare cases, GAS causes severe, life-threatening diseases. These are called "invasive" group A Streptococcus (iGAS) infections, meaning that the bacteria has entered deep tissues and organs, such as:

  • the lungs (pneumonia, lung abscess)
  • the muscles and their envelope (necrotizing fasciitis, also known as the "flesh-eating disease", which is a quickly progressing infection that destroys tissues under the skin)
  • other organs (the blood, lining around the brain and spinal cord, lining of the uterus after delivering a baby)
  • A streptococcal toxic shock syndrome can occur as part of an iGAS infection, when the bacteria produces toxins that can cause organs in the body to stop functioning properly

In rare instances, complications may occur following a GAS infection. These include:

  • acute post-streptococcal glomerulonephritis (a complication affecting the kidneys)
  • acute rheumatic fever (a complication that can affect the joints, heart, skin and central nervous system. It can result in a long-term heart condition called rheumatic heart disease)

About Group A streptococcal diseases

Some people carry the GAS bacteria as part of their normal skin, throat, vaginal or anal flora, with no signs or symptoms of infection.

iGAS develops when the GAS bacteria enter parts of the body where bacteria are not normally found, such as the blood, lungs, muscles, joints and bones, or the fluid surrounding the brain and spinal cord.

The spread of Group A streptococcus

GAS bacteria spreads from person to person, mainly through

  • Direct contact with a person with the bacteria or their nose, throat or wound secretions or objects contaminated with these secretions
  • Inhalation of respiratory droplets.

Transmission can occur from people infected with GAS, but also from people who carry the bacteria in the throat or on the skin without showing symptoms.

People who have a GAS infection are considered to be contagious until they have been treated with antibiotics for at least 24 hours.

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