Strep A
What is Strep A?
Group A streptococci (GAS) are bacteria commonly found in the throat and on the skin. The vast majority of GAS infections are relatively mild illnesses, such as strep throat and impetigo. Occasionally, however, these bacteria can cause much more severe and even life threatening diseases such as necrotizing fasciitis and streptococcal toxic shock syndrome (STSS). In addition, people may carry group A streptococci in the throat or on the skin and have no symptoms of disease.
Cause
Group A streptococcal pharyngitis is an infection of the oropharynx caused by Streptococcus pyogenes (group A strep bacteria).
The incubation period of group A strep pharyngitis is approximately 2 to 5 days.
Risk factors
Anyone can get group A strep pharyngitis, but age and close contact can increase someone's risk of infection.
Age
Group A strep pharyngitis is most common among children 5 through 15 years of age. It's rare in children younger than 3 years of age.
Close contact
Close contact with another person with strep throat is the most common risk factor for illness.
Contact with children: Parents of school-age children and adults who are often in contact with children are at increased risk.
Crowded settings can increase the risk for spreading the bacteria. These settings include:
- Daycare centers and schools
- Detention or correctional facilities
- Homeless shelters
- Military training facilities
Clinical features
Acute pharyngitis symptoms
It commonly presents with
- Fever
- Pain with swallowing
- Sudden onset of sore throat
On clinical examination, patients with group A strep pharyngitis usually have
- Anterior cervical lymphadenopathy
- Palatal petechiae
- Pharyngeal and tonsillar erythema
- Tonsillar hypertrophy with or without exudates
Patients with group A strep pharyngitis may also present with a scarlatiniform rash. The resulting syndrome is scarlet fever.
Less common symptoms
Other symptoms, especially among children, may include:
- Abdominal pain
- Headache
- Nausea and vomiting
Subacute illness
Respiratory disease caused by group A strep infection in children younger than 3 years of age rarely manifests as acute pharyngitis. Instead, these children usually have what is called “streptococcal fever” or “streptococcosis,” which involves mucopurulent rhinitis followed by:
- Anorexia
- Fever (but rarely high)
- Irritability
Diagnosis
Differential diagnosis
The differential diagnosis of acute pharyngitis includes multiple viral and bacterial pathogens. Viruses are the most common cause of pharyngitis in all age groups.
Experts estimate that group A strep, the most common bacterial cause, causes
- 20% to 30% of pharyngitis episodes in children
- 5% to 15% of pharyngitis infections in adults
Clinical examination only with viral symptoms
History and clinical examination can be used to diagnose viral pharyngitis when clear viral symptoms are present. These patients don't need testing for group A strep bacteria.
No viral symptoms? Tests are needed
Testing and diagnosis
To confirm group A strep pharyngitis, healthcare providers need to use either
- A rapid antigen detection test (RADT)
- Throat culture
RADTs have high specificity for group A strep bacteria but varying sensitivities when compared to throat culture. Throat culture is the gold standard diagnostic test.
Positive RADT or culture
Healthcare providers can use a positive RADT or throat culture as confirmation of group A strep pharyngitis.
Negative RADT
Children older than 3 years: Healthcare providers should follow up a negative RADT with a throat culture. Have a mechanism in place to contact the family and initiate antibiotics if the back-up throat culture is positive. Giving antibiotics to children with confirmed group A strep pharyngitis can reduce their risk of developing acute rheumatic fever.
All other ages: Throat culture after a negative RADT isn't routinely indicated. Acute rheumatic fever is very rare in these age groups.
Treatment
Patients, regardless of age, who have a positive RADT or throat culture need antibiotics. Don't treat viral pharyngitis with antibiotics.
Benefits of antibiotics
Using a recommended antibiotic regimen to treat group A strep pharyngitis:
- Shortens the duration of symptoms
- Reduces the likelihood of transmission to close contacts
- Decreases the development of complications
Prevention
Hand hygiene
Good hand hygiene and respiratory etiquette can reduce the spread of group A strep bacteria.
Antibiotic treatment
Treatment with an appropriate antibiotic for 12 hours or longer limits a person's ability to transmit group A strep bacteria.
People with group A strep pharyngitis should stay home from work, school, or daycare until both of the following are met:
- They are afebrile
- At least 12–24 hours after starting appropriate antibiotic therapy
Goals of prevention
Group A strep prevention activities vary by disease, but generally focus on three important goals:
- Limit exposure and spread of bacteria
- Treat group A strep infections
- Use preventive antibiotics when appropriate
Prevention steps and strategies
Limit exposure and spread of bacteria
Many daily healthy habits can help prevent infections:
- Care for fungal infections
- Clean and care for wounds
- Cover coughs and sneezes
- Wash glasses, utensils, and plates after someone who's sick uses them
- Wash hands often
Take extra measures for impetigo
- Wash body and hair often with soap and clean, running water
- Wash the clothes, linens, and towels of anyone with impetigo every day
- Don't share clothes, linens, or towels with anyone who has impetigo
After items (dishes, linens) have been washed, they're safe for others to use.
Treat infections
Take antibiotics, if prescribed.
Antibiotics treat the infection and help prevent serious complications, like rheumatic fever. They also prevent the bacteria from spreading to others.
Use preventive antibiotics when appropriate
Close contacts of someone with a group A strep infection generally don't get antibiotics to prevent them from getting sick. People who live together are examples of close contacts.
However, rheumatic fever and serious infections are important exceptions.
Rheumatic fever
Preventive antibiotics help protect people with rheumatic fever from getting it again. They may need preventive antibiotics over a period of many years (often until 21 years old). Preventive antibiotics can include daily antibiotics by mouth or a shot into the muscle every few weeks.
Serious infections
For patients with a serious infection, healthcare providers may give antibiotics to close contacts if they
- Are 65 years or older
- Have other factors that increase their risk of getting a serious group A strep infection
Wound care tips
Step 1: Wash hands with soap and water or use an alcohol-based hand rub if washing isn't possible.
Step 2: Clean all minor cuts and injuries that break the skin (like blisters and scrapes) with soap and water.
Step 3: After cleaning, cover draining or open wounds with clean, dry bandages until they heal.
When to seek care: See a healthcare provider for punctures and other deep or serious wounds.
Protect wounds and infections
If you have an open wound or skin infection, avoid spending time in:
- Hot tubs
- Natural bodies of water (e.g., lakes, rivers, oceans)
- Swimming pools
Prevention guidelines
Prevention of rheumatic fever and diagnosis and treatment of acute streptococcal pharyngitis
American Heart Association