What is it?
Scarlet fever, or scarlatina, is an illness that brings on a rash covering most of the body, a strawberry-like appearance of the tongue and usually a high fever. The most common source of scarlet fever is one form of a common bacterial infection known as strep throat. Scarlet fever is almost always accompanied by a sore throat and other signs and symptoms of a typical strep throat infection.
Scarlet fever is most common in children 5 to 15 years of age. Although scarlet fever was once considered a serious childhood illness, antibiotic treatments have made it less threatening.
Nonetheless, if left untreated, scarlet fever (like strep throat) can result in more serious conditions that affect the heart, kidneys and other parts of the body.
If your child has scarlet fever, he or she may experience these common signs and symptoms:
- Red rash that looks like a sunburn and feels like sandpaper
- Red lines (Pastia's lines) in folds of skin around the groin, armpits, elbows, knees and neck
- Strawberry-like red and bumpy appearance of the tongue, often covered with a white coating early in the disease
- Flushed face with paleness around the mouth
- Fever of 101 F (38.3 C) or higher, often with chills
- Very sore and red throat, sometimes with white or yellowish patches
- Difficulty swallowing
- Enlarged glands in the neck (lymph nodes) that are tender to the touch
- Nausea or vomiting
The sore throat, enlarged lymph nodes and fever are likely to appear first, while the "scarlet" signs and symptoms of scarlet fever usually appear on the second day of illness. If your child has scarlet fever, the rash and flushing will likely begin on his or her face or neck, later spreading to the chest, trunk, arms and legs. The rash won't appear on the palms of the hands or soles of the feet.
The rash and the redness in the face and tongue usually last about a week. After these signs and symptoms have subsided, the skin affected by the rash often peels.
A bacterium called Streptococcus pyogenes, or group A beta-hemolytic streptococcus, causes scarlet fever. This is the same bacterial infection that causes strep throat, but the strain of bacteria causing scarlet fever releases toxins that produce the rash, Pastia's lines, flushed face and red tongue.
How the infection spreads
Strep bacteria that cause scarlet fever spread from one person to another by fluids from the mouth and nose. If an infected person coughs or sneezes, the bacteria can become airborne, or the bacteria may be present on things the person touches — a drinking glass or a doorknob. If you're near an infected person, you may inhale airborne bacteria. If you touch something an infected person has touched and then touch your own nose or mouth, you could pick up the bacteria.
The incubation period — the time between exposure and illness — is usually two to four days. If scarlet fever isn't treated, a person may be contagious for a few weeks even after the illness itself has passed. And someone may carry scarlet fever strep bacteria without being sick. Therefore, it's difficult to know if you've been exposed.
Scarlet fever strep bacteria can also contaminate food, especially milk, but this mode of transmission isn't as common.
Rare causes of scarlet fever
Rare causes of scarlet fever are other strains of Streptococcus pyogenes associated with either a skin infection (impetigo) or a uterine infection contracted during childbirth. These cases result in the characteristic fever, rash and other "scarlet" signs and symptoms but not those associated with a throat infection.
Children 5 to 15 years of age are more likely than are other people to get scarlet fever.
Scarlet fever strep bacteria spread more easily among people in close contact. If a child carries the bacteria, the disease can spread easily among family members or schoolmates.
Scarlet fever rarely results in serious complications, particularly if promptly and appropriately treated with antibiotics. But post-scarlet fever disorders may occur. These include:
- Rheumatic fever. Rheumatic fever is an inflammatory disease that can affect the heart, joints, skin and nervous system. Long-term effects may include damage to heart valves; other heart disorders; and a syndrome called Sydenham's chorea, which causes emotional instability, muscle weakness and jerky movements of the hands, feet and face. Appropriate treatment of strep bacteria infection greatly reduces the risk of rheumatic fever.
- Poststreptococcal glomerulonephritis. Poststreptococcal glomerulonephritis is inflammation of the kidneys that results from certain byproducts of strep bacteria infection. This disorder may cause long-term kidney disease.
- Pediatric autoimmune neuropsychiatric disorders associated with streptococcal infections (PANDAS). Research suggests that strep bacteria infection may cause an autoimmune response that worsens symptoms in children with certain disorders including obsessive-compulsive disorder, Tourette syndrome and attention-deficit/hyperactivity disorder (ADHD). The increased severity of symptoms usually is temporary, lasting from weeks to months before symptoms improve again.
Other complications that may result from untreated scarlet fever include:
- Bacterial infection of the blood (bacteremia)
- Ear infection (otitis media)
- Inflammation of the membranes and fluid that surround the brain and spinal cord (meningitis)
- Infection of the bone behind the ear (mastoiditis)
- Infection of the heart's inner lining (endocarditis)
- Inflammation of mucous membranes and buildup of fluids in the sinuses (sinusitis)
- Pus-filled sac (abscess) in the throat
- Skin infections
Your doctor will conduct an exam to determine the cause of your child's sore throat, rash and other symptoms. He or she will:
- Look at the condition of your child's throat, tonsils and tongue
- Feel your child's neck to determine if lymph nodes are enlarged
- Assess the appearance and texture of the rash
If your doctor suspects strep as the cause of your child's illness, he or she will also swab the back of your child's throat to collect material that may harbor strep bacteria. Tests for the strep bacterium are important because a number of conditions can cause the signs and symptoms of scarlet fever, and these illnesses may require different treatments. If there are no strep bacteria, then some other factor is causing the illness.
Your doctor may order one or more of the following laboratory tests:
- Throat culture. The sample from your child's throat is examined in a laboratory test in which the bacteria can thrive. Although this is a very reliable test, the results may take as long as two days.
- Rapid antigen test. Your doctor may also order a rapid antigen test, sometimes called a rapid strep test, which can detect foreign proteins (antigens) associated with strep bacteria infection. This test can be completed during a visit to your doctor's office. This test is less reliable than is a throat culture. If a rapid antigen test is negative, your doctor will probably order the throat culture to ensure an accurate diagnosis.
- Rapid DNA test. Your doctor may also be able to order a relatively new rapid test that uses DNA technology to detect strep bacteria from a throat swab in a day or less. These tests are at least as accurate as throat cultures, and the results are available sooner.