Scarlet fever is a disease caused by infection with the group A Streptococcus bacteria (the same bacteria that causes strep throat).
Causes, incidence, and risk factors
Scarlet fever was once a very serious childhood disease, but now is easily treatable. It is caused by the streptococcal bacteria, which produce a toxin that leads to the hallmark red rash of the illness.
The main risk factor is infection with the bacteria that causes strep throat. A history of strep throat or scarlet fever in the community, neighborhood, or school may increase the risk of infection.
The time between becoming infected and having symptoms is short, generally 1 - 2 days. The illness typically begins with a fever and sore throat.
The rash usually first appears on the neck and chest, then spreads over the body. It is described as "sandpapery" in feel. The texture of the rash is more important than the appearance in confirming the diagnosis. The rash can last for more than a week. As the rash fades, peeling (desquamation) may occur around the fingertips, toes, and groin area.
Other symptoms include:
- Abdominal pain
- Bright red color in the creases of the underarm and groin (Pastia's lines)
- General discomfort (malaise)
- Muscle aches
- Sore throat
- Swollen, red tongue (strawberry tongue)
Signs and tests
- Physical examination
- Throat culture positive for group A strep
- Rapid antigen detection (throat swab)
Antibiotics are used to kill the bacteria that causes the throat infection. This is crucial to prevent rheumatic fever, a serious complication of strep throat and scarlet fever.
With proper antibiotic treatment, the symptoms of scarlet fever should get better quickly. However, the rash can last for up to 2 - 3 weeks before it fully goes away.
Complications are rare with the right treatment, but can include:
- Acute rheumatic fever
- Bone or joint problems (osteomyelitis or arthritis)
- Ear infection (otitis media)
- Inflammation of a gland (adenitis) or abscess
- Kidney damage (glomerulonephritis)
- Liver damage (hepatitis)
Calling your health care provider
Call your health care provider if:
- You develop symptoms of scarlet fever
- Your symptoms do not go away 24 hours after beginning antibiotic treatment
- You develop new symptoms
Bacteria are spread by direct contact with infected people, or by droplets exhaled by an infected person. Avoid contact with infected people.
Bisno AL, Stevens DL. Streptococcus pyogenes. In: Mandell GL, Bennett JE, Dolin R, eds. Principles and Practice of Infectious Diseases. 7th ed. Philadelphia, Pa: Elsevier Churchill Livingstone; 2009:chap 198.
Gerber MA. Group A Streptococcus. In: Kliegman RM, Behrman RE, Jenson HB, Stanton BF, eds. Nelson Textbook of Pediatrics. 19th ed. Philadelphia, Pa: Saunders Elsevier; 2011:chap 176.