Scarlet fever, how much do you know?

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Scarlet fever is an acute respiratory infectious disease common to school-age children and adolescents caused by group A hemolytic streptococcus type B. Its main clinical manifestations are fever, angina and rash. Because group A streptococcus (GAS) infection can develop both purulent and non-purulent complications, treatment of acute infection is needed to prevent these complications. Regarding the evaluation and treatment of scarlet fever, let's take a look at it together!

1

Etiology and epidemiology

The causative agent of scarlet fever is GAS, and the bacterial body components of the bacteria themselves and the toxins and proteases they produce are involved in the pathogenic process, which can cause a series of purulent, toxic and allergic lesions. The disease can occur all year round, especially in winter and spring. The population is generally susceptible, but the incidence is more common in children, especially in children and adolescents aged 5 to 15 years, and the difference in incidence between children and adults may be due to the presence or lack of immunity.

GAS can be present in the nasal mucosa, adenoids and tonsils, and patients and bacteria are the main source of infection, mainly transmitted by air droplets, but also through skin wounds and birth canal infections, with an incubation period of generally 2-5 days.

2

Clinical manifestations

Scarlet fever is usually associated with acute pharyngitis, and patients may present with fever, sore throat, and lymphadenopathy in the neck. If the patient does not show symptoms of pharyngitis, the source of infection may be a wound or burn infected with GAS.

Rash is one of the most important symptoms of scarlet fever, and most appear from the first to second day of onset, and occasionally as late as day 5. Starting from behind the ears, the base of the neck and the upper chest, it spreads to the chest, back, upper limbs, and finally to the lower limbs within 1 day, and a few take several days to spread throughout the body. The typical rash is a dense and uniform punctate congestive rash of the size of a needle cap spread on the basis of hyperemia and redness of the skin throughout the body, and the hand pressure subsides completely, and it reappears after decompression. In the folds of the skin such as the armpits, elbows, and groin, the rash can be seen densely linear, called the "Pavillon line". Patients have facial congestion and flushing, may have a small number of point rashes, and appear pale around the mouth and nose, which is called "perioral pallor circle". At the beginning of the onset, the surface of the patient's tongue is covered with white moss, and the nipples are red and swollen, protruding above the white moss, most notably the tip of the tongue and the edges. After 2 to 3 days, the white moss begins to fall off, the tongue surface is smooth and fleshy red, and there may be superficial rupture, and the nipple is still protruding, called "bayberry tongue". When the rash occurs, the patient's body temperature will be higher, and when the rash is all over the body, the body temperature gradually decreases, the symptoms of poisoning disappear, and the rash recedes. Peeling begins within a week after the rash has subsided, and the order of the peeling sites is consistent with the order in which the rash appears. The trunk is mostly fur-like peeling, and large membranous peelings are more common in the thick parts of the soles of the palms of the hands, and fissure-like peeling of the nail terminal is typical. Peeling usually lasts 2 to 4 weeks without pigmentation.

3

Clinical evaluation and diagnosis

When scarlet fever is clinically suspected, a detailed history investigation and physical examination is required. In patients associated with pharyngitis, centor criteria, namely fever, absence of cough, pharyngeal exudate, cervical lymphadenopathy, and patient age (generally < 15 years), help determine the likelihood of strep throat.

Peripheral blood tests may have an elevated white blood cell count and neutrophil ratio, toxic particles may be seen in cytoplasm, higher in purulent complications, and eosinophilia after eruption.

Culture of secretions from throat swabs or other lesions, as well as rapid streptococcus tests, can detect the presence of GAS. It is important to note that rapid streptococcus testing is controversial in people over 45 years of age because they are more likely to be carriers and the prevalence is lower in this age group. For young patients with a high CENTOR score, a rapid streptococcus test is recommended to confirm the infection and start treatment.

Diagnosis of scarlet fever can be determined based on characteristic clinical presentation, elevated white blood cell count, gas from throat swabs, pus cultures, and history of exposure to patients with scarlet fever or angina. Needs to be differentiated from some viral diseases such as measles, chickenpox, and hand-foot-and-mouth disease.

4

Treatment and prevention

Since scarlet fever is an infection caused by GAS, antibiotic therapy is required, the main purpose of which is to quickly eliminate pathogenic bacteria and prevent complications caused by streptococcal infections. Penicillin or amoxicillin is the first-line agent. If the patient is allergic to penicillin, other antibiotics such as cephalosporins or clindamycin may be chosen.

Once scarlet fever is started with antibiotic therapy, it needs to be taken strictly according to the course of treatment and cannot be stopped early. Due to the use of antibiotics and health care measures, the prognosis of scarlet fever is good, and after diagnosis and initiation of antibiotic therapy, patients can return to normal activities after 24 hours of fever reduction.

At present, there are no specific prevention and control measures such as vaccines for scarlet fever, and comprehensive prevention and control measures such as isolation treatment, monitoring, cluster epidemic investigation and treatment, and health education need to be carried out around key places and key populations to reduce the incidence. For children under 15 years of age and adolescents, who are susceptible to scarlet fever, health education should be strengthened to improve their awareness of disease prevention.

Resources:

1.ardo S, Perera TB. Scarlet Fever. [Updated 2022 Jan 17]. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2022 Jan-.

2. Kong Dechuan, Jiang Xianjin, et al. Research progress on incidence trends, clinical features and pathogenic characteristics of scarlet fever[J].Chinese Journal of Infectious Diseases,2022,40(03):189-192.

3.[Ji Lianmei. Scarlet fever - antibiotics are the first choice[J].Parents must read, 2020(12):40-41.