This disease presents with a sore throat after which fever sets in. There is redness and swelling of the tongue with spots called ‘Strawberry tongue’. Small red spots may also be present inside the oral cavity, particularly on the soft palate called Forchheimer spots.

Scarlet fever is classically manifested by a punctuate erythematous rash that is most prominent over the trunk and inner aspects of the arms and legs [8]. The rash is a characteristic feature of scarlet fever. It presents within 12-72 hours after the fever sets in and appears as a fine, rough, red coloured rash that begins in the trunk and armpits and then progresses over to the face and the rest of the body. It typically blanches under pressure and when present on the face, it presents with erythema of the face leaving a pale circular area around the mouth, which is called circumoral pallor. This rash is characteristically prominent on skin folds, called Pastia lines.

Laboratory tests

• Complete blood count
• ESR
• Urinalysis
• Throat culture: According to the American Heart Association, signs of group A streptococci (GAS) are always found in throat cultures in acute infections [9]. 
• Anti-deoxyribonuclease B antibody titres
• Anti-streptolysin-O titres

Imaging 

Imaging studies are not required to diagnose scarlet fever.

Test results

On the basis of results of throat culture and antibody testing, a diagnosis can be made.

Most scientists recommend penicillins, like benzylpenicillin and phenoxymethylpenicllin as drugs of first choice for effective treatment of Streptococcus tonsillopharyngitis and scarlet fever [3]. Erythromycin may be considered as an alternative drug if patients are resistant or allergic to penicillin or 1st generation cephalosporins [10]. A 10 day course of the antibiotics is generally sufficient to treat the infection. Patients should also be kept isolated during the course of the disease to prevent transmission.

Scarlet fever has an excellent prognosis. The fever persists for 3 to 6 days and the rash begins to desquamate and peel off on its own, fading after around 6 days. The disease is completely eradicated from the body with the help of a 10 day course of antibiotics.

Scarlet fever is considered an infectious, toxin-mediated disease whose pathogenicity depends upon production of specific exotoxins [2].

Causative agent

The main causative agent of scarlet fever is a gram positive bacterium called Streptococcus pyogenes, which belongs to the β-hemolytic group A streptococci, and is a natural colonizer of the human nasopharynx and oral cavity. S. pyogenes causes the widest range of infectious diseases in humans among all known bacterial pathogens [3]. Other members of the group A streptococci are also implicated in causing scarlet fever.

Transmission

There has been a confirmed outbreak of person-to-person transmitted scarlet fever, and the main risk factor was having a relative with tonsillitis [4]. Transmission is mainly air borne; via inhaled aerosol droplets containing the infectious agents, but the illness can be also be food borne.

Incidence

Increases in scarlet fever above usual seasonal levels are currently being seen across the United Kingdom [5]. Worldwide, around 10% of people are likely to get a throat infection from group A streptococci, and only 10% of these people are likely to develop scarlet fever.

Age

Scarlet fever is a rare disease in adult patients [6]. It typically affects young children between 5-15 years. Usually as the child reaches 10 years of age and above, antibodies to GAS strains are developed and circulated in the body, making the child fairly immune to further infections by the same bacteria.

Sex

This disease affects males and females equally.

The infective organisms may be inhaled or ingested, and after infection by a strain of group A streptococci, an incubation period of 1 to 4 days takes place. The bacteria produce pyrogenic toxins that cause the characteristic rash and fever. According to a retrospective study conducted in Taiwan, the frequencies of pyrogenic exotoxin genes were 9.5% for speA, 81.0% for speB, 4.8% for speC, and 71.4% for speF in isolates from patients of scarlet fever [7]. Inflammatory process begins which contributes to the redness of the rash. Patients are infective both during this as well as the subclinical period.

Scarlet fever has no vaccine available. Because of the wide distribution of S. pyogenes in the general population and the lack of an effective vaccine, possibilities for prevention allowing a suitable protection for diseases due to S. pyogenes are very limited [3]. 

Scarlet fever is one of a variety of diseases caused by group A streptococcus (GAS) [1]. It may be endemic, epidemic or sporadic and indeed many outbursts throughout the world have been reported in the past years. Scarlet fever is usually associated with pharyngitis which is the primary mode of illness by species of the group A streptococci, and often occurs after a throat infection. Although it is now perfectly treatable with the help of antibiotics that target gram positive bacteria, scarlet fever was a source of high mortality in the past. 

Definition

Scarlet fever is a streptococcal disease characterized by a skin rash in children. It can be endemic, epidemic or sporadic [3].

Cause

It is caused by bacteria belonging to group A Streptococci, which are gram positive strains and many are normally present in the nasopharynx.

Signs and symptoms

Scarlet fever begins with a sore throat which then progresses to a fever and a characteristic rash all over the body. The tongue becomes bright red and is called strawberry tongue. The infection persists for 3-6 days and the rash begins to peel off after 5-6 days.

Diagnosis

Diagnosis can be made clinically if characteristic signs are present. Throat culture is considered gold standard for diagnosis and antibody testing can also aid the diagnosis.

Treatment

Treatment is a course of antibiotics for 8-10 days along with bed rest and avoidance of public places to reduce the chances of transmission.

1. Yang P, Peng X, Zhang D, Wu S, Liu Y, Cui S, Lu G, Duan W, Shi W, Liu S, Li J, Wang Q. Characteristics of group A Streptococcus strains circulating during scarlet fever epidemic, Beijing, China, 2011. Emerg Infect Dis. 2013 Jun;19(6):909-15. 
2. Silva-Costa C, Carriço JA, Ramirez M, Melo-Cristino J. Scarlet fever is caused by a limited number of Streptococcus pyogenes lineages and is associated with the exotoxin genes ssa, speA and speC. Pediatr Infect Dis J. 2014 Mar;33(3):306-10. 
3. Stock I. Streptococcus pyogenes--much more than the aetiological agent of scarlet fever. [Article in German]. Med Monatsschr Pharm. 2009 Nov;32(11):408-16. 
4. Fernández-Prada M, Martínez-Diz S, Colina López A, Almagro Nievas D, Martínez Romero B, Huertas Martínez J. Scarlet fever outbreak in a public school in Granada in 2012. An Pediatr (Barc). 2014 Apr;80(4):249-53.
5. Guy R, Williams C, Irvine N, Reynolds A, Coelho J, Saliba V, Thomas D, Doherty L, Chalker V, von Wissmann B, Chand M, Efstratiou A, Ramsay M, Lamagni T. Increase in scarlet fever notifications in the United Kingdom, 2013/2014. Uro Surveill. 2014 Mar 27;19(12):20749. 
6. Sandrini J, Beucher AB, Kouatchet A, Lavigne C. [Scarlet fever with multisystem organ failure and hypertrophic gastritis]. Rev Med Interne. May 2009;30(5):456-9
7. Wu PC, Lo WT, Chen SJ, Wang CC. Molecular characterization of Group A streptococcal isolates causing scarlet fever and pharyngitis among young children: a retrospective study from a northern Taiwan medical center. J Microbiol Immunol Infect. 2014 Aug;47(4):304-10. 
8. Robbins and Cotran. Pathologic Basis of Disease. 8th ed. Philadelphia, Pa: Saunders Elsevier, 2010. ISBN 978-1-4160-3121-5
9. Gerber MA, Baltimore RS, Eaton CB, Gewitz M, Rowley AH, Shulman ST, et al. Prevention of rheumatic fever and diagnosis and treatment of acute Streptococcal pharyngitis: a scientific statement from the American Heart Association Rheumatic Fever, Endocarditis, and Kawasaki Disease Committee of the Council on Cardiovascular Disease in the Young, the Interdisciplinary Council on Functional Genomics and Translational Biology, and the Interdisciplinary Council on Quality of Care and Outcomes Research: endorsed by the American Academy of Pediatrics. Circulation. Mar 24 2009;119(11):1541-51
10. Bass JW. Antibiotic management of group A streptococcal pharyngotonsillitis. Pediatr Infect Dis J. Oct 1991;10(10 Suppl):S43-9