Scarlet fever: symptoms and treatment

Scarlet fever is an infectious disease caused by bacteria. It is treated in a few days with antibiotics. With this treatment, complications are rare.

Scarlet fever mainly affects children aged about 2 to 15 years during the winter, often in small outbreaks that occur in schools. Scarlet fever is uncommon in children under 2 years of age, as they are protected by maternal antibodies transmitted during pregnancy. In adults, the disease is quite rare.

Like other infections, scarlet fever returned after the health crisis. The introduction of preventive measures (mask use, containment, removal, etc.) led to some decline in immunity. This then led to an increase in the number of cases when the situation returned to normal. Another finding by physicians is that many infections are no longer seasonal. While influenza can now strike in the summer, scarlet fever is no longer limited to the winter season, but can strike at any time.

Patients are contagious before symptoms appear

Scarlet fever is an infectious disease caused by a bacterium in the streptococcus family – beta-hemolytic streptococcus A – which is also responsible for strep throat and other infections. In the case of scarlet fever, this bacterium, which remains localised in the throat, begins to produce toxins that cause a skin rash on the body and tongue.

Scarlet fever is transmitted through the air, by coughing, sneezing or spitting during a conversation, or indirectly, from objects contaminated with secretions (glasses, toys, hands, etc.). Sick people in turn become contagious as soon as the bacteria settle in the throat, even before symptoms appear. This explains why epidemics can develop despite the isolation of patients. Most often, the incubation period is short (1 to 4 days), but sometimes it can be longer.

Angina pectoris and small red spots on the skin

Scarlet fever has a sudden onset of fever and is generally high (above 38.5°C), accompanied by angina and difficulty in swallowing. A characteristic rash appears 1 or 2 days after the onset of the sore throat. This rash begins in the flexion folds (armpits, elbow, groin)’.

It then spreads to other parts of the body, such as the upper chest, lower abdomen, face (except the area around the mouth) and even the whole body. The skin, which is covered with tiny red dots that feel grainy to the touch, becomes bright red. The rash may also be itchy.

At the same time, the tongue is covered with an off-white deposit, then becomes depalcified (areas of the tongue “lose” their papillae) and becomes bright red between days 6 and 8. Some patients may also complain of headaches, abdominal pain, nausea or vomiting. Others may present with milder forms of the disease, with a lower fever and pink rash confined to the flexural folds, but all present with angina.

A quick diagnostic test

In the case of scarlet fever, however, angina is caused by bacteria, most commonly streptococcus, especially in children aged 5 to 15 years. If there is still doubt after the clinical examination, the doctor should carry out a diagnostic test for streptococcal pharyngitis (TROD). This quick, painless test can show whether the sore throat is indeed group A bacterial vasculitis. To carry out the test, the doctor takes a sample from the tonsils using a large swab, which is then placed in a tube containing a reagent. A test strip is then immersed in this liquid.

If the test is positive, the doctor knows that the sore throat is bacterial, a sign of scarlet fever, and that antibiotic treatment is therefore necessary.
Six-day antibiotic treatment to avoid complications

Scarlet fever used to be considered a serious disease because of the complications it could cause, in particular rheumatic fever and heart disease. Antibiotics, but also the reduction in the infectivity of bacteria, have made it possible to change this perspective. However, it is still very important to treat the infection correctly if complications are to be avoided, as poor management of scarlet fever can have serious consequences. Indeed, the UK Health and Safety Executive (UKHSA) recently urged parents to be vigilant after five children under the age of 10 died within seven days of being diagnosed with strep A infection.

Treatment is based on a 6-day course of amoxicillin (penicillin family) antibiotics. It also limits infectivity to 24-36 hours once initiated. If you are allergic to penicillins, your doctor will prescribe other antibiotics. To be effective, treatment must be continued at the prescribed dose and for the prescribed duration. Thanks to this treatment, the fever and pain disappear quickly. The skin develops over a longer period of time, with scaling occurring between the seventh and fifteenth day after the onset of the disease. The tongue also returns to its normal colour.

Prevention through hygiene

There is no vaccine against scarlet fever. As with any communicable disease, prevention is based on hygiene measures that have been common knowledge since the Covid-19 pandemic. So make sure to wash your hands regularly with soap and water or, failing that, with hydroalcoholic gel, wear a mask, avoid close contact and disinfect transmission surfaces with, for example, 70°C alcohol. These strict hygiene rules should be applied from the very first signs of the disease.

Prescribing an antibiotic to prevent infection in contact persons is no longer recommended. However, it may be indicated for people at risk of complications (elderly, immunocompromised, chronically ill).