Scarlet Fever
Summary
Scarlet Fever is an acute infectious disease caused by Group A Streptococcus (GAS) - Streptococcus pyogenes that produces Erythrogenic (Pyrogenic) Exotoxins. It typically affects children aged 2-10 years and presents with Fever, Sore Throat (Streptococcal Pharyngitis/Tonsillitis), and a characteristic Sandpaper-like Erythematous Rash. The classic features include Strawberry Tongue (Initially white-coated with red papillae, then red with prominent papillae), Flushed Cheeks with Circumoral Pallor, and Pastia's Lines (Linear petechiae in skin creases). Treatment with Phenoxymethylpenicillin (Penicillin V) shortens illness duration, reduces complications, and prevents transmission. Scarlet Fever is a Notifiable Disease in the UK. Complications include Peritonsillar Abscess (Quinsy) and post-streptococcal sequelae (Rheumatic Fever, Post-Streptococcal Glomerulonephritis). There has been a resurgence of scarlet fever cases in the UK since 2014. [1,2,3]
Clinical Pearls
"Sandpaper Rash": The rash feels like sandpaper when you run your hand over it. Blanches on pressure.
"Strawberry Tongue": Initially white-coated with red papillae ("White Strawberry"), then sheds coating leaving red tongue with prominent papillae ("Red Strawberry").
"Circumoral Pallor": Flushed cheeks with a pale area around the mouth – Classic finding.
"Pastia's Lines": Linear petechiae in skin folds (Antecubital fossa, Axillae, Groin). Persist after rash fades.
Demographics
| Factor | Notes |
|---|---|
| Age | 2-10 years (Peak: 4-8 years). Rare less than 2 years (Maternal antibodies) and in adults (Immunity). |
| Season | Late Autumn/Winter/Spring. |
| Setting | Schools, Nurseries. Outbreaks occur. |
UK Resurgence
- Significant increase in cases since 2014.
- 2022: Record numbers reported (iGAS and scarlet fever).
- Reason unclear: Possible changes in circulating strains.
Transmission
- Respiratory Droplets: Coughing, Sneezing.
- Direct Contact: With infected secretions.
- Incubation Period: 2-4 days.
- Infectious Period: From symptom onset until 24 hours after starting antibiotics. Untreated: Infectious for 2-3 weeks.
Organism
- Streptococcus pyogenes (Group A Streptococcus – GAS).
- Gram-positive cocci in chains.
- M protein (Virulence factor – Antiphagocytic).
- Produces Erythrogenic Exotoxins (SPE A, B, C) which cause the rash.
Mechanism
- Pharyngeal Infection: GAS colonises pharynx/tonsils.
- Toxin Production: Erythrogenic toxins released.
- Toxin Sensitivity: Rash develops in individuals who do NOT have antibodies to the toxin. (Once immune, no rash with subsequent infections).
- Systemic Toxin Effects: Fever, Vascular damage (Rash, Strawberry tongue).
Why Only Some Get Scarlet Fever?
- Not all GAS strains produce erythrogenic toxins.
- Individuals with pre-existing antitoxin antibodies won't develop the rash (But can still get strep throat).
| Condition | Key Features |
|---|---|
| Scarlet Fever | Sandpaper rash, Strawberry tongue, Pastia's lines, Sore throat. |
| Viral Exanthem (Morbilliform) | Viral prodrome, NO sandpaper texture, Confluent maculopapular. |
| Kawasaki Disease | Fever ≥5 days, Conjunctivitis, Strawberry tongue, Polymorphous rash, Extremity changes. |
| Drug Eruption | Recent drug exposure. Morbilliform. |
| Staphylococcal Scalded Skin Syndrome | Younger children, Tender erythema, Nikolsky positive, Skin peeling. |
| Toxic Shock Syndrome (TSS) | Very unwell, Hypotension, Multi-organ involvement. |
| Measles | Koplik spots, Cough, Coryza, Conjunctivitis, Rash spreads head→body. |
Symptoms (Timeline)
| Day | Feature |
|---|---|
| Day 1 | Acute onset: Fever (Often high – 38.5-40°C), Sore throat, Headache, Malaise, Nausea/Vomiting. |
| Day 1-2 | Tonsillitis/Pharyngitis (Exudative). Tender anterior cervical lymphadenopathy. |
| Day 1-2 | Strawberry Tongue appears (White coating with red papillae). |
| Day 2 | Rash appears: Starts on neck/chest → Spreads to trunk/limbs. Sandpaper texture. |
| Day 5-7 | Rash fades. Desquamation (Skin peeling) begins, especially on fingertips/toes. |
| Week 2 | Desquamation continues. May last weeks. |
Rash Characteristics
| Feature | Notes |
|---|---|
| Appearance | Fine, Punctate, Erythematous papules on erythematous base. |
| Texture | Sandpaper-like (Rough to touch). |
| Distribution | Trunk, Limbs, Flexures. Spares palms/soles. |
| Blanching | Yes – Blanches on pressure. |
| Accentuation | In skin folds (Axillae, Groin, Antecubital fossae). |
| Pastia's Lines | Linear petechiae in skin folds. Persist after rash fades. |
Facial Features
| Feature | Notes |
|---|---|
| Flushed Cheeks | Red cheeks. |
| Circumoral Pallor | Pale area around the mouth. |
| Strawberry Tongue | Day 1-2: White coating with red papillae. Day 4-5: Red tongue with prominent papillae (Coating sheds). |
Diagnosis
- Clinical Diagnosis: Based on characteristic features.
- Throat Swab: Culture for GAS (Gold standard but takes 24-48h). Rapid Antigen Detection Test (RADT) available (Quick but less sensitive).
- ASO Titres (Anti-Streptolysin O): Not useful acutely. Used to confirm recent strep infection (Post-streptococcal complications).
Blood Tests (If Unwell)
| Test | Rationale |
|---|---|
| FBC | WCC (Neutrophilia). Eosinophilia during convalescence. |
| CRP | Elevated. |
| Blood Cultures | If invasive GAS (iGAS) suspected. |
Management Algorithm
SUSPECTED SCARLET FEVER
(Fever, Sore throat, Sandpaper rash, Strawberry tongue)
↓
CLINICAL ASSESSMENT
- Confirm rash characteristics
- Examine throat (Exudative tonsillitis)
- Cervical lymphadenopathy
- Check for red flags (Shock, Respiratory distress, Cellulitis)
↓
RED FLAGS (iGAS)?
┌────────────────┴────────────────┐
YES (Sepsis, Necrotising Fasciitis) NO (Uncomplicated)
↓ ↓
**HOSPITAL ADMISSION** OUTPATIENT MANAGEMENT
IV Antibiotics ↓
Urgent senior review
↓
ANTIBIOTIC TREATMENT
┌──────────────────────────────────────────────────────────┐
│ FIRST-LINE: │
│ **Phenoxymethylpenicillin (Penicillin V)** │
│ - Child 1-5 years: 125mg QDS for 10 days │
│ - Child 6-11 years: 250mg QDS for 10 days │
│ - Child ≥12 years/Adult: 500mg QDS for 10 days │
│ │
│ PENICILLIN ALLERGY: │
│ - Clarithromycin │
│ - Or Erythromycin │
│ - Or Azithromycin (3-day course) │
└──────────────────────────────────────────────────────────┘
↓
SUPPORTIVE CARE
- Paracetamol / Ibuprofen for fever and pain
- Fluids
- Soft diet if sore throat
↓
INFECTION CONTROL
- Exclusion from school/nursery until 24h after starting antibiotics
- Hand hygiene
- Notify Public Health (NOTIFIABLE DISEASE)
Why 10 Days?
- Prevents Rheumatic Fever (Post-streptococcal complication).
- Eradicates carriage.
Notification
- Scarlet Fever is a NOTIFIABLE DISEASE in the UK.
- Report cases to local Health Protection Team/UKHSA.
Suppurative (Local Extension)
| Complication | Notes |
|---|---|
| Peritonsillar Abscess (Quinsy) | Unilateral tonsillar swelling, Trismus, "Hot potato" voice. Needs drainage. |
| Otitis Media | Ear pain. |
| Sinusitis | Facial pain. |
| Cervical Lymph Node Abscess | Fluctuant neck swelling. |
Non-Suppurative (Post-Streptococcal)
| Complication | Timing | Notes |
|---|---|---|
| Acute Rheumatic Fever (ARF) | 2-4 weeks post-infection | Carditis, Polyarthritis, Chorea, Erythema marginatum, Subcutaneous nodules. Rare in UK. Jones criteria. |
| Post-Streptococcal Glomerulonephritis (PSGN) | 1-3 weeks post-infection | Haematuria, Oedema, Hypertension. Usually self-limiting. Low C3. |
| PANDAS | Variable | Paediatric Autoimmune Neuropsychiatric Disorders Associated with Streptococcal infections. Controversial. |
Invasive Group A Strep (iGAS)
| Complication | Notes |
|---|---|
| Sepsis | Bacteraemia. Requires IV antibiotics. |
| Necrotising Fasciitis | Rapidly spreading soft tissue infection. Surgical emergency. |
| Streptococcal Toxic Shock Syndrome | Hypotension, Multi-organ failure. High mortality. |
| Factor | Notes |
|---|---|
| Uncomplicated Scarlet Fever | Excellent prognosis with antibiotics. Symptoms resolve within 1 week. |
| Desquamation | Normal part of recovery. May last 2-3 weeks. |
| Complications | Rare with prompt antibiotic treatment. |
| iGAS | Serious. Significant morbidity/mortality if invasive disease. |
Key Guidelines
| Guideline | Organisation | Key Recommendations |
|---|---|---|
| Scarlet Fever Management | UKHSA (2022) | Penicillin V for 10 days. Notification required. Exclusion 24h after starting antibiotics. |
| Sore Throat Guidelines | NICE NG84 | FeverPAIN/Centor scores. Antibiotic prescribing. |
Key Points
- 10-Day Course: Essential to prevent Rheumatic Fever.
- Notification: Legal requirement.
- 2022 Surge: Increased awareness of iGAS risk.
What is Scarlet Fever?
Scarlet Fever is an infection caused by bacteria called Group A Streptococcus. It usually starts with a sore throat and fever, followed by a red, rough rash that feels like sandpaper.
Who gets it?
Mainly children aged 2-10 years. It spreads through coughs, sneezes, and close contact.
What does the rash look like?
- Red, fine spots that feel rough like sandpaper.
- Starts on the neck and chest, then spreads.
- The tongue may look like a strawberry (Red with bumps).
- Cheeks are flushed with a pale area around the mouth.
Is it serious?
Most cases are mild and treated easily with antibiotics. However, it can rarely lead to more serious infections or complications affecting the heart or kidneys. That's why we treat with antibiotics for a full 10 days.
Can my child go to school?
Your child should stay home until they have taken antibiotics for at least 24 hours and feel well enough to attend.
Do I need to tell anyone?
Yes. Scarlet Fever is a notifiable disease, so we will report it to Public Health. This helps them track outbreaks.
Primary Sources
- UK Health Security Agency. Scarlet fever: symptoms, diagnosis and treatment. GOV.UK. 2022.
- Shulman ST, et al. Clinical practice guideline for the diagnosis and management of group A streptococcal pharyngitis. Clin Infect Dis. 2012;55(10):e86-102. PMID: 22965026.
- Lamagni T, et al. Resurgence of scarlet fever in England, 2014-16. Lancet Infect Dis. 2018;18(2):180-187. PMID: 29191628.
Common Exam Questions
- Rash Description: "Describe the rash of Scarlet Fever."
- Answer: Fine, Erythematous, Punctate papules with Sandpaper texture, Blanching, Accentuated in skin folds (Pastia's Lines).
- Tongue Finding: "What is the classic tongue appearance?"
- Answer: Strawberry Tongue – White coating with red papillae (Early), then Red with prominent papillae (Late).
- Facial Finding: "What facial feature is characteristic?"
- Answer: Circumoral Pallor (Flushed cheeks with pale area around mouth).
- Antibiotic and Duration: "What is the treatment and why 10 days?"
- Answer: Penicillin V for 10 days. To prevent Rheumatic Fever.
Viva Points
- Post-Streptococcal Glomerulonephritis: Occurs 1-3 weeks post-infection. Unlike Rheumatic Fever, NOT prevented by antibiotics.
- Notifiable Disease: Must report to UKHSA.
- iGAS Awareness: 2022 surge. Be alert to sepsis, necrotising fasciitis.
- Desquamation: Skin peeling in convalescence is normal (Not a sign of worsening).
Medical Disclaimer: MedVellum content is for educational purposes and clinical reference. Clinical decisions should account for individual patient circumstances. Always consult appropriate specialists.