Scarlet fever

Scarlet Fever

• Group A strep live in the nose and throat and can easily spread to other people.
• It is important to know that all infected people do not have symptoms or seem sick.
• People who are infected spread the bacteria by coughing or sneezing, which creates small respiratory droplets that contain the bacteria.

Scarlet fever

Streptococcus pyogenes, which is also called group A Streptococcus or group A strep, cause scarlet fever.

Etiology

• Scarlet fever is an illness caused by pyrogenic exotoxin-producing S. pyogenes.
• S. pyogenes are gram-positive cocci that grow in chains.
• They exhibit β-hemolysis (complete hemolysis) when grown on blood agar plates.
• They belong to group A in the Lancefield classification system for β-hemolytic Streptococcus, and thus are called group A streptococci.

Clinical Features

• Scarlet fever, also called scarlatina, is characterized by a scarlatiniform rash and usually occurs with group A strep pharyngitis.
• It can also follow group A strep pyoderma or wound infections.

Scarlet fever with slapped cheek and white mustache look

Rash

Characteristics of the rash typically include:

• Erythematous rash that blanches on pressure
• Sandpaper quality
• Accentuation of the red rash in flexor creases (i.e., under the arm, in the groin), termed “Pastia’s lines”
• Begins on the trunk, then quickly spreads outward, usually sparing the palms, soles, and face
• The rash usually persists for about one week and desquamation may follow.
• In addition, the face may appear flushed and the area around the mouth may appear pale (i.e., circumoral pallor).
• A yellowish white coating with red papillae may initially cover the tongue.
• The eventual disappearance of the coating can result in a “strawberry tongue.”

Measles and Scarlet Fever

Transmission

• Group A strep infections, including scarlet fever, are most commonly spread through direct person-to-person transmission.
• Typically transmission occurs through saliva or nasal secretions from an infected person.
• People with scarlet fever are much more likely to transmit the bacteria to others than asymptomatic carriers.
• Crowded conditions — such as those in schools, daycare centers, or military training facilities — facilitate transmission.
• Although rare, spread of group A strep infections may also occur via food.
• Foodborne outbreaks of group A strep have occurred due to improper food handling.
• Fomites, such as household items like plates or toys, are very unlikely to spread these bacteria.

=Reservoir

Humans are the primary reservoir for group A strep.

Treatment with an appropriate antibiotic for 24 hours or longer generally eliminates a person’s ability to transmit group A strep. People with scarlet fever should stay home from work, school, or daycare until:

• They are afebrile AND
• 24 hours after starting appropriate antibiotic therapy

Incubation Period

The incubation period of scarlet fever is approximately 2 through 5 days.

Risk Factors

Scarlet fever can occur in people of all ages. It is most common among children 5 through 15 years of age. It is rare in children younger than 3 years of age.

The most common risk factor is close contact with another person with scarlet fever. Crowding, such as found in schools, military barracks, and daycare centers, increases the risk of disease spread.

Diagnosis and Testing

The differential diagnosis of scarlet fever with pharyngitis includes multiple viral pathogens that can cause acute pharyngitis with a viral exanthema. Clinicians need to use either a rapid antigen detection test (RADT) or throat culture to confirm scarlet fever with pharyngitis. RADTs have high specificity for group A strep but varying sensitivities when compared to throat culture. Throat culture is the gold standard diagnostic test. Clinicians should follow up a negative RADT in a child with symptoms of scarlet fever with a throat culture. Clinicians should have a mechanism to contact the family and initiate antibiotics if the back-up throat culture is positive.

Treatment

The use of a recommended antibiotic regimen to treat scarlet fever:

• Shortens the duration of symptoms
• Reduces the likelihood of transmission to family members, classmates, and other close contacts
• Prevents the development of complications, including acute rheumatic fever

Penicillin or amoxicillin is the antibiotic of choice to treat scarlet fever. There has never been a report of a clinical isolate of group A strep that is resistant to penicillin. For patients with a penicillin allergy, recommended regimens include narrow-spectrum cephalosporins (e.g., cephalexin, cefadroxil), clindamycin, azithromycin, and clarithromycin.

Table: Antibiotic Regimens Recommended for Group A Streptococcal Pharyngitis

Table: Antibiotic Regimens Recommended for Group A Streptococcal Pharyngitis

Drug, Route	Dose or Dosage	Duration or Quantity
For individuals without penicillin allergy
Penicillin V, oral	Children: 250 mg twice daily or 3 times daily; adolescents and adults: 250 mg 4 times daily or 500 mg twice daily	10 days
Amoxicillin, oral	50 mg/kg once daily (max = 1000 mg); alternate: 25 mg/kg (max = 500 mg) twice daily	10 days
Benzathine penicillin G, intramuscular	<27 kg: 600 000 U; ≥27 kg: 1 200 000 U	1 dose
For individuals with penicillin allergy
Cephalexin,a oral	20 mg/kg/dose twice daily (max = 500 mg/dose)	10 days
Cefadroxil,a oral	30 mg/kg once daily (max = 1 g)	10 days
Clindamycin, oral	7 mg/kg/dose 3 times daily (max = 300 mg/dose)	10 days
Azithromycin,b oral	12 mg/kg once daily (max = 500 mg)	5 days
Clarithromycinb, oral	7.5 mg/kg/dose twice daily (max = 250 mg/dose)	10 days

Prognosis and Complications

Rarely, complications can occur after scarlet fever. Scarlet fever can have the same suppurative and non-suppurative complications as group A strep pharyngitis. Suppurative complications result from local or hematogenous spread of the organism. They can include:

• Peritonsillar abscesses
• Retropharyngeal abscess
• Cervical lymphadenitis
• Invasive group A strep disease

Acute rheumatic fever is a nonsuppurative sequelae of group A strep pharyngitis. Post-streptococcal glomerulonephritis is a nonsuppurative sequelae of group A strep pharyngitis or skin infections. These complications occur after the original infection resolves and involve sites distant to the initial group A strep infection site. They are thought to be the result of the immune response and not of direct group A strep infection.

Prevention

Good hand hygiene and respiratory etiquette can reduce the spread of all types of group A strep infection. Hand hygiene is especially important after coughing and sneezing and before preparing foods or eating. Good respiratory etiquette involves covering your cough or sneeze. Treating an infected person with an antibiotic for 24 hours or longer generally eliminates their ability to transmit the bacteria. Thus, people with scarlet fever should stay home from work, school, or daycare until:

• They are afebrile AND
• At least 24 hours after starting appropriate antibiotic therapy

Epidemiology and Surveillance

• Humans are the only reservoir for group A strep.
• It is most common among children 5 through 15 years of age.
• It is rare in children younger than 3 years of age.
• In the United States, scarlet fever is most common during the winter.

Scarlet fever Resources
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