What Is Scarlet Fever?

Overview

Scarlet fever, typically a childhood disease, is an infection characterised by its ‘scarlet’-coloured rash.¹ This infection is caused by a bacteria known as Streptococcus pyogenes, also known as group A streptococcus (GAS).²

Previously a life-threatening condition due to its potential complications,³ scarlet fever is now easily treated in the community through the use of antibiotics and supportive care.

Epidemiology

Scarlet fever is a disease that mainly affects children. To put this into perspective, 10-year-old children make up 90% of the cases of scarlet fever, with children ages 2-8 being the most commonly affected¹. This is thought to be because most children do not develop immunity to the GAS bacteria until the age of 10.⁴ This reasoning also explains why adults are rarely affected by scarlet fever.

Scarlet fever can take anywhere between one day and a week to begin to cause symptoms. These symptoms are short-lived, typically lasting for a week. However, since scarlet fever is highly contagious and capable of causing severe health complications, it is encouraged to seek help from your GP if you suspect yourself or anyone around you to have scarlet fever. People are generally considered contagious up until 24 hours after starting antibiotic treatment or until their symptoms resolve.¹

Causative agent

Group A streptococcus (GAS) is a bacteria that is typically found in the upper respiratory tract; this region refers to the nose, mouth and throat.^5,6 Some people are carriers for GAS, meaning the bacteria lives within their upper respiratory tract, however they do not experience symptoms.⁷ Meanwhile, GAS may cause various infections in others, for example

• Skin infections (e.g. cellulitis, impetigo).
• Throat infections (e.g. pharyngitis/strep throat, tonsillitis).

Both skin and throat infections caused by GAS can lead to the development of scarlet fever.³

Since GAS lives in the nose, mouth and throat, it may be spread by any method that allows others to come into contact with mucus or saliva. These methods may include coughing, sneezing, airborne droplets and poor hand hygiene, to name a few.¹

Symptoms

Scarlet fever may first be suspected in a child presenting with a sore throat and a fever. These are the most common initial symptoms of this infection, especially in children below the age of 5.⁸

Naturally, scarlet fever is characterised by the ‘scarlet’ rash it causes. This is a red, ‘sandpaper-like’ rash, which is typically first seen on the chest and gradually spreads to the arms and legs. This rash may also be visible on the cheeks, giving a child a ‘flushed appearance’.⁸

It is important to note that in individuals with darker skin, the rash may not present with its distinct scarlet colour. The rash may be described to have more of a ‘sunburnt appearance’, while still maintaining its sandpaper-like texture.⁸

Other symptoms may include:⁸

• Strawberry tongue - This is a white coating that appears on the tongue during the early days of the illness. This coating eventually peels away, revealing a swollen, red and bumpy tongue - resembling a strawberry.⁹
• Swollen neck glands.
• Nausea, vomiting, and stomach pain.
• Headache.
• Itchy, peeling skin.

While it is important to be aware of how scarlet fever presents so that it can be identified early, it is also important to be aware of other conditions that present similarly.

• Measles.
• Rubella.
• Erythema infectiosum.
• Kawasaki disease.
• Drug allergies may also cause skin rashes.⁸

Diagnosis

Due to its characteristic presentation, formal tests are not usually required to diagnose someone with scarlet fever. Clinicians can typically identify scarlet fever on the basis of a patient’s symptoms.

In specific circumstances where

• The diagnosis is uncertain
• The patient is allergic to penicillin
• Or the patient is particularly vulnerable to complications

A throat swab may be offered to identify the GAS bacteria and identify the best antibiotic to give to the patient.⁸

Treatment

Treating scarlet fever involves early identification and early administration of antibiotics. The emphasis on early treatment is based on reducing the chances of an individual experiencing complications. 

The golden standard of treatment for scarlet fever is a type of penicillin called phenoxymethylpenicillin. This is given for a course of 10 days for both children and adults.

For patients who are allergic to penicillin, alternative antibiotics like clarithromycin, azithromycin and erythromycin may be provided. Which antibiotic is the most suitable depends on various factors, such as age, pregnancy, and side effects.

Alongside antibiotics, patients are encouraged to engage in supportive care. This involves encouraging rest, recovery, and prevention of the spread of scarlet fever. Some examples of supportive care include

• Bed rest.
• Drinking lots of fluids.
• Handwashing and proper hygiene.
• Painkillers - can help with sore throat, fever and headache.
• Antihistamines and ointments - may help with itchiness and skin irritation/peeling.⁸

Complications

Early treatment of scarlet fever is heavily encouraged due to its potentially fatal complications. The main complications to be cautious of include

• Rheumatic fever.
• Kidney damage (in the form of post-streptococcal glomerulonephritis).¹⁰

Rheumatic fever is a complication in which the body’s immune system begins to attack healthy parts of the body rather than the GAS bacteria itself. This misdirected attack leads to inflammation across various systems in the body, causing fever and affecting the joints, skin, brain and heart. Inflammation in the joints is known as arthritis and most commonly affects knees, elbows, ankles and wrists. Inflammation of the heart can lead to symptoms of heart failure, contributing to the following symptoms:

• Chest pain.
• Shortness of breath.
• Racing heart.
• Tiredness.¹¹

To simplify the name, post-streptococcal glomerulonephritis (PSG) describes inflammation of a structure inside the kidneys known as the ‘glomerulus’ following an infection from group A streptococcus. Similarly to rheumatic fever, this is not an infection. Rather, PSG is the result of the effects of the immune system misdirecting its attack onto the kidneys rather than onto the infection itself.

PSG usually presents around 10 days after scarlet fever begins to cause symptoms. It may present with the following:

• Dark urine and decreased urine output.
• Swelling in various parts of the body.
• Fatigue.¹²

Other noteworthy complications are:

• Sinusitis.
• Meningitis.
• Pneumonia.
• Sepsis.¹³

If you or anyone you know is experiencing the above symptoms, it is vital that you seek medical assistance as soon as possible. Both of these complications can lead to significant impairment and, if left unresolved for a prolonged period of time, can lead to chronic disease or, worse, death.

Prevention

When it comes to prevention, there are two main approaches: 

• Preventing the spread of scarlet fever to people who are uninfected (primary prevention).
• Preventing the development of complications in people who are already infected (secondary prevention).

Methods of primary prevention include:

• Good hand hygiene.
• Cover your nose and mouth when coughing or sneezing.
• Disposing of used tissues.
• Encouraging self-isolation for infected individuals. This period of self-isolation should last until either 24 hours after antibiotic treatment has started or until symptoms have resolved.¹³

The main methods of secondary prevention of scarlet fever are early diagnosis and effective antibiotic treatment. Effective antibiotic treatment involves clinicians identifying the most appropriate antibiotic for the infected individual and patients finishing the full course of antibiotics. This method of prevention aims to reduce the risk of developing complications of scarlet fever and enables a quicker recovery.⁸

Summary

Scarlet fever is primarily a childhood disease, caused by group A streptococcus bacteria (GAS).Its most characteristic symptoms include a sore throat, fever, and of course, its ‘scarlet’ rash.It may take up to 5 days post-infection to start experiencing these symptoms. Therefore, it is important to maintain good hygiene and take precaution during this time.Diagnosis often relies on a patient’s clinical presentation, rather than formal testing.Once diagnosed, a patient will be commenced on antibiotics, typically penicillin.

Early identification and treatment of scarlet fever is at the heart of patient safety. This is as it reduces the risk of developing complications, and enables quicker recovery.

FAQs

What is scarlet fever?

Scarlet fever is a bacterial childhood infection caused by Group A Streptococcus bacteria (GAS). This can develop from conditions such as strep throat.

What are the common symptoms of scarlet fever?

Common symptoms include a sore throat, fever, red sandpaper-like rash, swollen neck glands, and a "strawberry tongue". Some may also experience nausea, vomiting, and headaches.

How is scarlet fever transmitted?

Scarlet fever is contagious and spreads through airborne droplets created when an infected person coughs or sneezes. It can also be transmitted through contact with contaminated surfaces or objects, emphasising the importance of good hand hygiene.

Who is at risk of getting scarlet fever?

Anyone, including adults, can get scarlet fever. However, it is most common in children below the age of 10. People with strep throat are more susceptible to developing scarlet fever if left untreated.

How is scarlet fever diagnosed?

A diagnosis is typically made on the basis of an individual's clinical features. In cases where the diagnosis is uncertain, a GP may request a throat swab to identify the GAS bacteria, and identify the most suitable antibiotic to prescribe.

What is the treatment for scarlet fever?

Typically, scarlet fever is treated with antibiotics like penicillin. It is important to complete the entire course of antibiotics even if symptoms improve, to prevent complications and the spread of the infection.

Can scarlet fever lead to complications?

If left untreated, scarlet fever can lead to complications like rheumatic fever or kidney inflammation (post-streptococcal glomerulonephritis). Prompt identification and effective antibiotic treatment can prevent these complications.

How can i prevent scarlet fever?

Preventing scarlet fever involves practising good hand hygiene, covering your mouth and nose when coughing or sneezing, and self-isolation. Effectively treating strep throat can also help prevent scarlet fever.

Can i go to school or work with scarlet fever?

Individuals with scarlet fever are typically considered contagious until they have been on antibiotics for at least 24 hours and/or their symptoms have resolved. If you are unsure as to whether or not you or your child can return to work or school, make sure to contact your GP or workplace for their guidance.

Is scarlet fever a serious disease?

Scarlet fever can be serious if left untreated, due to its potential complications. However, with early diagnosis and proper treatment, most people experience excellent recovery.

Can you get scarlet fever more than once?

It is possible to get scarlet fever more than once, but it's relatively rare since most people develop an immunity to the GAS bacteria.

This FAQ is solely to provide a quick reference for some of the questions most frequently asked about scarlet fever. If you suspect you or someone you know has scarlet fever, it's essential to arrange an appointment with your GP for prompt diagnosis and treatment.