Scarlet fever

Scarlet fever is an infectious disease caused by specific bacteria, namely streptococci. Typically, it manifests itself in a sore throat with fever and a scarlet rash, however the rash is not always present. Treatment with antibiotics reduces the risk of spread, but it does not prevent long-term effects from streptococcal infections.

At a glance

  • Scarlet fever is a bacterial infection with streptococci.
  • Typical symptoms are a sore throat, high fever, a scarlet skin rash, and a tongue that is first grayish-white and then strawberry-red.
  • Scarlet fever mainly affects children between the ages of six and twelve.
  • The same pathogens can cause inflammation of the throat and tonsils (angina tonsillaris) without a rash and many other infections.
  • Antibiotics are typically used to treat the disease.
  • Without antibiotics, the risk of spread is higher and the course of the disease lasts a little longer.

Note: The information in this article cannot and should not replace a medical consultation and must not be used for self-diagnosis or treatment.

Scarlet fever: a baby’s arm has a red skin rash.

What is scarlet fever?

Scarlet fever is a typical childhood disease caused by streptococci. However, these bacterial pathogens also occur in adults. Scarlet fever can occur several times, even after removal of the adenoids. Affected children have a fever, sore throat, and a scarlet rash. However, the typical rash only occurs with those strains of bacteria that produce certain toxins (pyrogenic exotoxins). 

The disease can be treated well with antibiotics and the contagiousness of those affected can be reduced, so that community facilities may be visited again sooner. Long-term effects of an infection by scarlet fever bacteria can be permanent damage to joints, heart, and kidneys. However, this occurs very rarely in Central Europe at present. The ability of antibiotic treatment to reduce these long-term effects from scarlet fever has not been proven. 

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What are the symptoms of scarlet fever?

The first symptoms appear one to three days after infection. Typical symptoms are a sore throat with difficulty swallowing, high fever, chills and indisposition. The lymph nodes in the neck may be severely swollen. Young children in particular also suffer from abdominal pain and vomiting.  

A special form is febrile scarlet fever, in which the rash is localized near a skin site/wound that is infected with scarlet fever bacteria.  

The disease looks different, depending on which strain of bacteria is present:  

Scarlet fever 

Only when the bacteria produce certain toxins does the raised scarlet rash develop. It begins on the first or second day of illness in the armpits and groin and spreads as subtle spots over the entire body. The palms and soles are not affected, and typically the region around the mouth is pale. A rash may also appear on the mucous membranes of the mouth (enanthem). Initially, white coatings are visible on the tongue, then the tongue turns dark red. This is why it is also referred to as “strawberry tongue”.

After six to nine days, the rash disappears again. A few days later, the skin peels, initially fine (powdery) on the face, and later coarse, especially on the palms of the hands and soles of the feet. Mild courses of scarlet fever, in which some of the above symptoms are absent, are called atypical scarlet fever (scarlatinella).

Important: Because scarlet fever bacteria have different toxins and the body only ever builds immunity to one strain of bacteria and/or the toxin it produces, children can get scarlet fever more than once. 

Pharyngitis and/or tonsillitis  

The disease progresses without a rash if the bacteria do not produce scarlet fever toxins. There is then an inflammation of the tonsils (angina tonsillaris) and the mucous membranes of the throat and pharynx (pharyngitis) with fever, chills, and indisposition. Symptoms vary in severity: some people have a high fever and purulent tonsillitis, while some show only mild symptoms.  

Other pathologies caused by scarlet fever bacteria

The same bacteria that cause scarlet fever can also cause superficial as well as deep skin and tissue infections. Less commonly, they are also the cause of pneumonia, joint infections, bone infections, meningitis, middle ear infections, and blood poisoning. 

Important: In some people (strep carriers), the scarlet fever bacteria are present in the throat without causing symptoms. The likelihood that other people will become infected with it is extremely low. However, people who are acutely ill can transmit the bacteria to other people.

Which pathogens cause scarlet fever?

Scarlet fever is caused by the bacterial strain Streptococcus pyogenes. It belongs to the so-called group A streptococci. There are different types of streptococci, many of which can colonize the skin and mucous membranes of humans and animals, even without causing symptoms. However, among the beta-hemolytic group A strep, there are many disease-causing types, including Streptococcus pyogenes.  

Streptococcus pyogenes is found all over the world and primarily affects humans. In very close contact with humans, the bacteria can also survive in dogs and cats, potentially making them a source of infection.

What are the risk factors of scarlet fever?

Since scarlet fever pathogens are found in large numbers in the throat, especially in an acute inflammation, they become airborne when people talk, sneeze, or cough and spread through droplet infection. Most people become infected through direct contact with sick people, for example when a sick person coughs on them. In rare cases, however, contaminated objects, food, or water can also transmit the pathogens. 

Important: If affected persons are already immune to certain bacterial toxins, a typical skin rash does not appear. Nevertheless, they can spread the scarlet fever pathogens further if they fall ill with tonsillitis or a skin infection.

How common is scarlet fever?

Scarlet fever is one of the most common bacterial infections in children. It mostly affects 6 to 12-year-olds. Additionally, throat infections caused by A streptococci occur in all age groups. In Germany, approximately one to one and a half million streptococcal throat infections occur each year. Children in community facilities are particularly affected during the colder months of the year.

Scarlet fever is one of the most common bacterial infections in children. It mostly affects 6 to12-year-olds.

What complications can occur with scarlet fever?

Scarlet fever pathogens (group A strep) primarily colonize the throat. If they are able to multiply unhindered during an infection, they spread via the mucous membranes. Typical complications include inflammation of the lymph nodes, the soft tissues of the throat, the middle ear, and the lungs. In this context, a boil (abscess) or even blood poisoning (sepsis) can develop.

In Germany, long-term effects caused by scarlet fever bacteria, which can be severe, occur less frequently:

Acute kidney inflammation

Acute kidney inflammation occurs mainly in children between the ages of 2 to 10, about one to five weeks after infection with streptococci. The inflammatory reaction makes the kidney permeable to larger blood components. This can cause the urine to turn brown and become foamy. In addition, affected individuals often have a fever as well as abdominal pain, back pain and headaches. Permanent damage to the kidney may result.

Acute rheumatic fever 

Acute rheumatic fever occurs primarily in children and adolescents ages 3 to 16, about two to three weeks after the sore throat has subsided. Inflammation occurs throughout the body, primarily affecting the heart and large joints, as well as the skin and nervous system. Patients also have a fever and feel very weak. Severe, permanent damage such as heart valve defects can develop.

How can scarlet fever be prevented?

There is no vaccine against scarlet fever. Avoid contact with sick people who are still contagious. Frequent and careful hand washing with soap also prevents infection. Items such as toys can be easily disinfected because scarlet fever pathogens are relatively sensitive to environmental agents.  

Persons suffering from a severe underlying disease or immune deficiency can be protected against infection with preventive antibiotic therapy if the risk of infection is high. In patients suffering from a secondary streptococcal disease, a new streptococcal infection is prevented by a long-term prophylaxis.

How is scarlet fever diagnosed?

Scarlet fever can often be recognized by the typical symptoms. Doctors can use a rapid test to detect streptococci in a throat swab in the doctor’s office. When taking the swab, it is important to swab thoroughly over both tonsils and, if possible, also the back of the throat wall. If the swab result is negative or unclear, the doctor will send another swab to a laboratory that will prepare a bacterial culture.

If doctors suspect that long-term effects of scarlet fever are present, they will take a blood sample to check whether certain antibodies against the pathogen Streptococcus pyogenes are detectable. 

How is scarlet fever treated?

Bed rest, fever-reducing painkillers, and gargling alleviate the symptoms. Doctors usually prescribe penicillin or a similar antibiotic that is effective against the pathogen. It is essential to take this medication as prescribed for five to ten days, even if the symptoms have already disappeared. Otherwise, a relapse could occur.  

Important: Antibiotic treatment not only eliminates the pathogens and symptoms. Antibiotics also shorten the time in which affected persons can infect others, so that they are allowed to visit community facilities again more quickly.

There are other measures to prevent the spread of this contagious disease: 

Measures for the acutely ill 

Persons who are ill with scarlet fever or another infection with Streptococcus pyogenes must not visit or work in community facilities. Parents of affected children must inform community facilities. 

Twenty-four hours after the first dose of an effective antibiotic, the patient is no longer contagious and attending community facilities is again permitted. However, if acutely ill persons do not receive antibiotics, they may not visit or work in community facilities again until the symptoms have completely subsided. The attending physician must make this assessment. However, written re-admission is not necessary.  

Measures for contact persons

No special measures are necessary if contact is made with persons who have an uncomplicated case of the illness. However, contact persons should be made aware of the risk of infection so that they can seek treatment immediately if symptoms occur.

Reviewed by the German Society for Pediatric Infectiology (Deutsche Gesellschaft für Pädiatrische Infektiologie e.V.).

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