Group A Streptococcus Infections

  • Medical Author:
    Charles Patrick Davis, MD, PhD

    Dr. Charles "Pat" Davis, MD, PhD, is a board certified Emergency Medicine doctor who currently practices as a consultant and staff member for hospitals. He has a PhD in Microbiology (UT at Austin), and the MD (Univ. Texas Medical Branch, Galveston). He is a Clinical Professor (retired) in the Division of Emergency Medicine, UT Health Science Center at San Antonio, and has been the Chief of Emergency Medicine at UT Medical Branch and at UTHSCSA with over 250 publications.

  • Medical Editor: Melissa Conrad Stöppler, MD
    Melissa Conrad Stöppler, MD

    Melissa Conrad Stöppler, MD

    Melissa Conrad Stöppler, MD, is a U.S. board-certified Anatomic Pathologist with subspecialty training in the fields of Experimental and Molecular Pathology. Dr. Stöppler's educational background includes a BA with Highest Distinction from the University of Virginia and an MD from the University of North Carolina. She completed residency training in Anatomic Pathology at Georgetown University followed by subspecialty fellowship training in molecular diagnostics and experimental pathology.

Just a Sore Throat or Strep Slideshow

Are group A strep infections contagious?

In general, group A strep infections are contagious, but there are some qualifiers to this answer. For example, strep throat is contagious, but other infection types such as toxic shock syndrome are generally considered noncontagious; consequently, the answer depends on the specific type of infection and any extenuating circumstances.

What is the contagious period for group A strep infections?

For those infections that are considered to be contagious, the person is contagious in the incubation period (before any symptoms of the infection develop) and through the acute phase of the infection while the patient has symptoms. When symptoms stop, the person is usually noncontagious unless the individual becomes a carrier (colonized with group A strep but without symptoms).

What is the incubation period for group A strep infections?

The incubation period for GAS pharyngitis and cellulitis varies from about one to five days. Other types of GAS infection may develop rapidly (necrotizing fasciitis) while others (scarlet fever) may take a week or more to develop.

What are the symptoms and signs of GAS infections?

GAS infections can produce many different signs and symptoms:

  • Pharyngitis (strep throat/tonsillitis): sore throat, irritation with swallowing, white patches on tonsils (exudates), swollen lymph nodes on the neck, fever; pharyngitis with fever and white patches on tonsils are important but not definitive signs of GAS pharyngitis.
  • Scarlet fever: pharyngitis symptoms (see above), pastia (pink or red lines formed of confluent petechiae, which are small purple or red spots in the skin caused by minor blood vessel breaks) that are found in skin creases, especially the flexor surface of the elbow), fever, rash on neck and chest, then entire body with sandpaper texture, muscle aches, abdominal pain, swollen red tongue (strawberry tongue)
  • Rheumatic fever: inflammation of the joints, heart valve damage
  • Glomerulonephritis: inflammation of the kidneys, impaired kidney function
  • Necrotizing fasciitis: tissue destruction that progresses rapidly
  • Toxic shock syndrome: rapidly progressing organ failure with low blood pressure

Most of the diseases listed here for GAS infection usually occur after an initial pharyngitis, with necrotizing fasciitis and toxic shock sometimes occurring without a detectable initial pharyngitis infection. Other disease processes involving GAS organisms (for example, meningitis, bone infections, pneumonia, wound infections, and others) produce the typical symptoms associated with these disease processes and clinically are not unique for GAS or other pathogenic organisms.

Picture of a Streptococcus pyogenes (Strep throat) infection
Figure 2: Picture of a Streptococcus pyogenes (Strep throat) infection. SOURCE: CDC/Dr. Heinz F. Eichenwald
Medically Reviewed by a Doctor on 2/19/2016
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