1. What are the different types of diseases that Group A strep causes?

Streptococcus pyogenes are gram-positive cocci that grow in chains. They are β -hemolytic, meaning that they exhibit a clear zone of hemolysis when grown on blood agar plates. They belong to group A in the Lancefield classification system for β-hemolytic Streptococcus, and thus are also called group A Streptococcus. Group A Streptococcus can cause a variety of infections, the most common of which is streptococcal pharyngitis or strep throat. Group A Streptococcus can also cause scarlet fever, skin infections like impetigo and cellulitis, non-suppurative complications of streptococcal infections such as acute rheumatic fever and post-streptococcal glomerulonephritis, and invasive diseases such as pneumonia, septic arthritis, septicemia, meningitis, necrotizing fasciitis, streptococcal toxic shock syndrome, and musculoskeletal and surgical wound infections.

2. What causes the rash of scarlet fever?

Scarlet fever, or scarlatina, is a strep infection that occurs with a characteristic scarlatiniform rash. The characteristic rash is red with fine papules (“sandpaper”), appearing initially on the trunk and spreading peripherally over hours to days to cover almost the entire body. Most often scarlet fever occurs with streptococcal pharyngitis but it can occur with streptococcal wound infections or impetigo. It is caused by a particular strain of group A Streptococcus that produces a pyrogenic exotoxin, which leads to the rash.

3. Should we treat patients just based on the scarlatiniform rash?

Because the differential diagnosis of scarlet fever includes viral pharyngitis with a viral exanthema and other mucocutaneous syndromes such as Kawasaki Disease and Stevens-Johnson syndrome (SJS), the diagnosis of scarlet fever should be confirmed with a rapid antigen detection test (i.e. rapid strep test) performed on a throat swab or throat culture prior to antibiotic treatment.

4. If a patient has a positive strep test, do we have to treat?

CDC encourages clinicians to follow the Infectious Diseases Society of America (IDSA) 2012 Clinical Practice Guidelines for the Diagnosis and Management of Group A Streptococcal Pharyngitis. These are national, evidence-based recommendations regarding how to diagnose and treat streptococcal pharyngitis.

Streptococcal pharyngitis is usually self-limited, even if not treated with antibiotics. However, IDSA recommends treatment with antibiotics for patients with streptococcal pharyngitis because it speeds recovery, limits transmission of group A Streptococcus to others, and most importantly, decreases the risk of acute rheumatic fever and suppurative complications (e.g., peritonsillar abscess, mastoiditis).

It is important to emphasize that IDSA recommends treatment for patients with symptomatic streptococcal pharyngitis that has been confirmed to be due to group A Streptococcus using a positive rapid antigen detection test (also called a rapid strep test) or throat culture. This is because asymptomatic colonization with group A Streptococcus is very common. In the winter, as many as 20% (1 in 5) of children can be asymptomatically colonized in the oropharynx with group A Streptococcus and will test positive by rapid strep test or throat culture. However, children with asymptomatic colonization typically do not need antibiotic treatment; these children do not have symptoms, are much less likely to transmit group A Streptococcus to others, and are very unlikely to develop suppurative or nonsuppurative complications, such as acute rheumatic fever.

A rapid strep test or throat culture should only be performed in children who have signs and symptoms of streptococcal pharyngitis. Because colonization is common, testing children who do not have signs and symptoms of strep throat leads to many false positives and unnecessary antibiotic use. IDSA states that patients with clear viral symptoms—including cough, runny nose, hoarseness, oral ulcers, conjunctivitis—do not need to be tested for group A Streptococcus because these are symptoms of viral pharyngitis.

Antibiotics have risks too—including allergies, side effects, and promotion of antibiotic resistance. Correctly selecting the patients who need a strep test can help us protect our patients from avoidable adverse drug events and antibiotic resistance.

5. Some children keep getting recurrent streptococcal pharyngitis. Why is that?

It is not uncommon to see a child several times a year with sore throat and positive test results for group A Streptococcus. Many children who appear to have recurrent streptococcal pharyngitis actually have recurrent episodes of viral pharyngitis and are asymptomatically colonized with group A Streptococcus. They test positive for group A Streptococcus because they are colonized. Repeated antibiotic treatment in these children is unnecessary because they are less likely to transmit group A Streptococcus to others and are very unlikely to develop complications. However, identifying carriers can be difficult. How to determine whether someone is a carrier is addressed in the Infectious Diseases Society of America guidelines and the Red Book.

6. What are the signs/symptoms of group A Streptococcus infection?

The main signs and symptoms of streptococcal pharyngitis are sore throat with a sudden onset, pain with swallowing, and fever. Streptococcal pharyngitis also commonly presents with patchy exudates on the tonsils and anterior cervical lymphadenopathy. Streptococcal pharyngitis may include headache, abdominal pain and vomiting, but these symptoms occur in the presence of sore throat symptoms.

Streptococcal pharyngitis does not cause cough, runny nose, hoarseness, oral ulcers or conjunctivitis. These are symptoms that more commonly occur with viral pharyngitis, and therefore neither strep testing nor antibiotics are needed for patients with these symptoms.

7. What ages commonly get strep pharyngitis?

Streptococcal pharyngitis is most common among children 5 to 15 years of age, but it can occur in adults. It is very rare in children younger than 3 years of age, as streptococcal disease in children less than 3 years of age rarely manifests as pharyngitis. Instead, young children with group A Streptococcus infection may get a mucopurulent rhinitis associated with fever, irritability, and poor appetite.

8. Which ages groups should be tested for strep pharyngitis?

Streptococcal pharyngitis is most common among children 5 through 15 years of age. Because children less than 3 years of age rarely get streptococcal pharyngitis and acute rheumatic fever is very rare in children less than 3 years, IDSA guidelines recommend against routinely testing children less than 3 years of age for streptococcal pharyngitis, as this may lead to false-positive tests and unnecessary antibiotic use. In select symptomatic children less than 3 years of age who have other risk factors for GAS pharyngitis, such as children who have an older sibling with confirmed streptococcal pharyngitis, IDSA guidelines state that testing can be considered.

9. What is the risk of scarlet fever in adults?

Scarlet fever can occur in adults if infected with the strain of group A Streptococcus that produces a pyrogenic exotoxin. However, scarlet fever is most common in children 5 to 15 years of age.

10. Is there any benefit to treating patients <2 years old?

The vast majority of children less than 3 years of age should not be tested for streptococcal pharyngitis, as this can lead to false-positive tests and unnecessary antibiotic use. In select children less than 3 years of age, such as symptomatic children who have an older sibling with confirmed streptococcal pharyngitis, IDSA guidelines state that testing can be considered.

11. When do you treat asymptomatic siblings of a child with a positive strep test? Is there a lower age limit for that? (I.e. would you treat a 6 month-old who’s 4 yea- old sibling has strep?)

IDSA guidelines specifically recommend against streptococcal testing or treating asymptomatic household contacts of patients with streptococcal pharyngitis. One-third of household contacts of children with streptococcal pharyngitis will become symptomatic, in which case testing and treatment is indicated. However, studies have shown that treating asymptomatic household contacts with penicillin is not effective at preventing them from later developing symptomatic streptococcal pharyngitis. Treating asymptomatic household contacts needlessly exposes them to the risks of antibiotics without benefiting them.

12. Is there a website/poster that is available from the CDC that we can share with our colleagues or patient families?

For more information about group A Streptococcus, please visit: http://www.cdc.gov/groupastrep/diseases-public/index.html

For more information about appropriate antibiotic use and the Get Smart: Know When Antibiotics Work Program, please visit: http://www.cdc.gov/getsmart/ Shulman ST, Bisno AL, Clegg HW, et al. Clinical practice guideline for the diagnosis and management of group A streptococcal pharyngitis: 2012 update by the Infectious Diseases Society of America. Clin Infect Dis. 2012;55(10):e86–102.

Committee on Infectious Diseases. Group A streptococcal infections. In Kimberlin DW, Brady MT, Jackson MA, Long SS, editors. 30th ed. Red Book: 2015 Report of the Committee on Infectious Diseases. Elk Grove Village (IL): American Academy of Pediatrics; 2015:732–44.

Questions answered by: Katherine Fleming-Dutra, MD, Craig Shapiro, MD, and Chris Van Beneden, MD MPH.

Dr. Fleming-Dutra is a pediatric emergency physician with the Get Smart: Know When Antibiotics Program in the Office of Antibiotic Stewardship at the Centers for Disease Control and Prevention (CDC). Dr. Shapiro is pediatric infectious diseases physician and director of the Antibiotic Stewardship Program at Children’s Healthcare of Atlanta. Dr. Van Beneden is a medical epidemiologist and expert on group A Streptococcus in the Respiratory Diseases Branch in the Division of Bacterial Diseases at CDC.