Scarlet Fact Sheet

Definition Scarlet fever (sometimes called scarlatina) is a notifiable infectious disease caused by the bacteria pyogenes, also known as group A streptococcus (GAS). The characteristic clinical features include a sore throat, fever, and extensive red, sandpaper-like . Pathophysiology Scarlet fever is caused by toxin-producing strains of Streptococcus pyogenes, also known as Group A streptococcus (GAS). GAS bacteria can colonise the throat or skin. Asymptomatic pharyngeal carriage of S.pyogenes occurs in 3–23% of healthy children. When GAS cause , the primary site is usually the throat resulting in pharyngitis. The rash and fever associated with scarlet fever are due to exotoxin release by the bacteria.

Scarlet fever is highly contagious and is transmitted when a person's mouth, throat, or nose comes into contact with infected saliva or mucus (such as on cups, utensils, pencils, toys, or surfaces), or by aerosol transmission. Outbreaks in nurseries, schools and other institutions where there is close contact between individuals can occur. The incubation period is usually 2–3 days but can range from 1–6 days. Prevalence Scarlet fever can occur at any age but is most common in children between 2–8 years of age, with a peak incidence at 4 years of age. Incidence is seasonal, and in the UK most cases occur in the winter and spring months. Although scarlet fever is much less common than it used to be, recent years have seen a substantial increase in incidence. In England there are usually 3,000–4,000 cases diagnosed each year but in 2013–14 more than 14,000 cases were notified. Public Health England data show that increased levels of scarlet fever infection are continuing. Between September 2014–March 2015, 5,746 cases were reported in England compared with 2,833 cases during the same period in 2013–14. On average in England in 2014–15, there were 10.7 cases of scarlet fever reported per 100,000 population.

Prognosis Although scarlet fever is usually a mild and self-limiting illness, prompt treatment is needed to significantly reduce the risk of complications. In most cases, the clinical features of the infection, including the rash, resolve over about 1 week. Peeling of the skin, in particular of the tips of the digits may occur when the rash has resolved. Once the person has had scarlet fever, they are unlikely to contract it again, but they are still susceptible to other forms of streptococcal infection. Complications Complications of scarlet fever are now rare and can be categorized into suppurative and non- suppurative. Suppurative complications are due to spread of the infection and tend to occur early in the infection. They include: • . • Throat infection and abscess (peritonsillar , , ).

Scarlet Fever Fact Sheet October 2019 Scarlet Fever Fact Sheet • Acute and mastoiditis. • Streptococcal pneumonia. • Meningitis and cerebral abscess. • Endocarditis, , and . • and streptococcal (invasive Group A streptococcal ). Non-suppurative (autoimmune) complications tend to occur later in the course of infection, particularly (but not exclusively) in untreated people. They include: • Acute rheumatic fever — this is an immunologically-mediated response and can cause carditis and endocarditis (leading to valvular heart disease), reactive arthritis, and skin complaints (such as marginatum). • Streptococcal glomerulonephritis — this typically occurs 2 weeks or more after acute/initial infection, and presents with haematuria, reduced urine output, peripheral oedema, proteinuria, and hypertension. Permanent damage is rare. Presentation The diagnosis of scarlet fever is usually made on the basis of characteristic clinical features alone. The first clinical features are often non-specific and include: • Sore throat. • Fever (typically greater than 38.3°C). • , fatigue, , and vomiting. • A blanching rash usually develops on the abdomen and chest 12–48 hours after initial symptoms, before spreading to the neck, limbs, and extremities. • The rash is characteristically red, generalized and punctate with a rough, sandpaper-like texture. • The rash is particularly florid in the skin folds of the neck, axillae, groin, elbows, and knees (Pastia's lines). • The skin (in particular at the tips of the digits) may peel (desquamate) after the rash resolves. Examination may also reveal: • Strawberry tongue — initially the tongue is covered with a white coat through which red papillae may be seen. Later, the white covering disappears, leaving the tongue with a beefy red appearance. • Swollen cervical . • Flushed face, with marked circumoral pallor. • Pharyngitis, and red macules dotted over the hard and soft palate (Forchheimer spots).

Reference: NICE CKS Scarlet Fever https://cks.nice.org.uk/scarlet-fever#!management Accessed October 2019

Scarlet Fever Fact Sheet October 2019