[1] The signs and symptoms include a sore throat, fever, headache, swollen lymph nodes, and a characteristic rash.

[7] Scarlet fever develops in a small number of people who have strep throat or streptococcal skin infections.

[1] In the early 20th century, scarlet fever was a leading cause of death in children, but even before World War II and the introduction of antibiotics, its severity was already declining.

[1] However, not all cases present with a fever, the degree of tiredness may vary, the sore throat and tongue changes might be slight or absent, and in some the rash can be patchy rather than diffuse.

[5][page needed] Cough, hoarseness, runny nose, diarrhea, and conjunctivitis are typically absent in scarlet fever; such symptoms indicate what is more likely a viral infection.

[22] The complications, which can arise from scarlet fever when left untreated or inadequately treated, can be divided into two categories: suppurative and nonsuppurative.

[citation needed] In the second case, the streptococcal infection may spread through the lymphatic system or the blood to areas of the body further away from the pharynx.

[17] Strep throat spreads by close contact among people, via respiratory droplets (for example, saliva or nasal discharge).

[26][21] The strains of group A streptococcus that cause scarlet fever need specific bacteriophages for there to be pyrogenic exotoxin production.

[21] There are two methods used to confirm suspicion of scarlet fever; rapid antigen detection test and throat culture.

[22] Serologic testing seeks evidence of the antibodies that the body produces against the streptococcal infection, including antistreptolysin-O and antideoxyribonuclease B.

[12] Other conditions that might appear similar include impetigo, erysipelas, measles, chickenpox, and hand-foot-and-mouth disease, and may be distinguished by the pattern of symptoms.

[5] One of the main goals of treatment is to prevent the child from developing one of the suppurative or nonsuppurative complications, especially acute rheumatic fever.

[34] Tonsillectomy, although once a reasonable treatment for recurrent streptococcal pharyngitis, is not indicated, as a person can still be infected with group A streptococcus without their tonsils.

Previously, observed resistance rates had been 10–30%; the increase is likely the result of overuse of macrolide antibiotics in recent years.

[10] New research published in October 2020 indicates that the bacterium appears to be getting more robust after being infected with viruses,[10] specifically the North-East Asian serotype M12 (emm12) (group A Streptococcus, GAS).

[45] They found three new genes, acquired from viruses, which cause development of "superantigens" targeting white blood cells, resulting in a more virulent strain of the bacterium.

[10] A vaccine that will protect against the 180 to 200 types of bacteria causing the disease has been worked on for over 20 years, but as of 2020[update] a safe one had not yet been developed.

[50] The World Health Organization has reported an increase in scarlet fever (and iGAS – invasive GAS cases) in England, and other European countries during this time.

[52] In late December 2022, the CDC's Health Alert Network issued an advisory on the reported increases in invasive GAS infections.

[55] The first unambiguous description of the disease in the medical literature appeared in the 1553 book De Tumoribus praeter Naturam by the Sicilian anatomist and physician Giovanni Filippo Ingrassia, where he referred to it as rossalia.

The first unequivocal description of scarlet fever appeared in a book by Joannes Coyttarus of Poitiers, De febre purpura epidemiale et contagiosa libri duo, which was published in 1578 in Paris.

[citation needed] In 1675 the term that has been commonly used to refer to scarlet fever, "scarlatina", was written by Thomas Sydenham, an English physician.

[citation needed] The association between streptococci and disease was first described in 1874 by Theodor Billroth, discussing people with skin infections.

[56] Also in 1884, the German physician Friedrich Loeffler was the first to show the presence of streptococci in the throats of people with scarlet fever.

The association between streptococci and scarlet fever was confirmed by Alphonse Dochez and George and Gladys Dick in the early 1900s.

[57] Also in 1884, the world's first convalescent home for people with scarlet fever was opened at Brockley Hill, Stanmore, founded by Mary Wardell.

[60][61][62][63] Scarlet fever serum from horses' blood was used in the treatment of children beginning in 1900 and reduced mortality rates significantly.

[64] In 1906, Austrian pediatrician Clemens von Pirquet postulated that disease-causing immune complexes were responsible for the nephritis that followed scarlet fever.

[32] The incidence of scarlet fever was reported to be increasing in countries including England, Wales, South Korea, Vietnam, China, and Hong Kong in the 2010s; the cause had not been established as of 2018.