Scarlet Fever is a disease caused by the bacteria Streptococcus pyogenes. Scarlet fever usually occurring in children, but can also affect adults. The most common and well-known disease caused by this bacteria is Strep Throat. Scarlet fever usually occurs after a case of Strep throat that was not treated with antibiotics. Rarely, scarlet fever can occur without a known or recognized illness of strep throat. Occasionally, scarlet fever can occur at the beginning or soon after the onset of strep throat. When it does, it can be a presenting sign along with the sore throat and fever of strep throat. Scarlet fever was historically a very common illness of childhood. Currently, scarlet fever is rarely seen because of the widespread use of antibiotics for treating Strep throat.
Scarlet fever is usually a mild illness with a rash and fever. This illness can be treated easily with antibiotics. Children with scarlet fever can sometimes recover without antibiotics. Treatment is important to decrease the risk of infection spreading to the blood, which is called sepsis. Treatment is also needed to prevent the complication of rheumatic fever and rheumatic heart disease. With treatment, the prognosis is excellent. Children generally recover unless there is an underlying immune deficiency.
Signs and Symptoms
- The symptoms of scarlet fever often, but not always, include the symptoms of strep throat.
- The symptoms of strep throat are a painful, sore throat, and fever.
- There is a noticeable absence of other cold symptoms, such as runny nose, cough, and sneezing, which accompanies viral causes of sore throat.
- The throat will be a bright red, but sometimes may just have red spots on the back of the throat or palate, called palatal petechiae.
- Usually, but not always, a white phlegmy substance (called exudate), can be seen on the tonsils. *Some adults also experience headache as a separate symptom of strep throat, unrelated to the fever.
- Some people may have abdominal pain with strep throat. This complaint is more common in children. This may be due to one of the toxins of Streptococcus or it may be due to mesenteric lymphadenitis, an enlargement of the lymph nodes surrounding the intestines, sometimes causing pain.
- With scarlet fever, a red rash appears on the skin, mostly on the chest and abdomen. This rash sometimes concentrates especially around the groin region. This red rash is how scarlet fever got its name. The rash may spread to cover most of the body. It looks like a lacy rash, pink to red in color. The rash that accompanies scarlet fever is sometimes called a scarlatiniform rash, which literally means a rash that looks like scarlet fever. (Scarlet fever was called scarlatina historically). The rash sometimes has a rough texture like sandpaper. This so-called "sandpaper rash" may be present over the area where the visible red rash is. Sometimes, the sandpaper texture of skin may be present on areas of the skin where the rash is not found. When pressed, the rash loses its red color. This is called "blanching." A rash that does not blanch is due to hemorrhage (bleeding under the skin), bruises, or some other illness other than scarlet fever. A non-blanching rash is worrisome as it may indicate meningococcemia, an infection of the covering around the brain. This infection also causes a fever and rash but is much more of an emergency and has a far worse prognosis if not treated immediately.
- Other signs of scarlet fever include dark red lines in the folds of the skin. These are called Pastia lines and are usually seen along the folds of the inner elbows or other joints. Scarlet fever also typically is associated with a bright strawberry-red tongue. The tongue also has slightly swollen papillae (the bumps on the tongue), giving it the appearance of a strawberry texture. This symptom is called "strawberry tongue."
- Lastly, as a person recovers from the illness, desquamation (peeling of the skin) may occur in areas where the rash was. Desquamation is usually most prominent on the skin of the hands.
Scarlet fever is caused by Streptococcus pyogenes, also known as Group A streptococcus (GAS). This is the same bacteria that causes strep throat and rheumatic fever. In rare cases, scarlet fever is due to Staphylococcus aureus.
- Scarlet fever can be recognized easily by an experienced physician. However, for scarlet fever, it is important to perform some tests to confirm the diagnosis.
- A rapid strep test involves swabbing the throat with a Dacron swab. The test takes less than five minutes to perform and get results, so it can be done immediately in the clinic or ER. A positive test confirms the diagnosis with a 99% of true cases of GAS infection (this means that 1% of people who do not have the infection will test positive for it). A negative test shows that the illness is not present in 90% of those tested (this means 10% of those who actually have the infection will test negative). It is possible that the throat infection has completely resolved prior to the onset of scarlet fever. In this situation, the bacteria will no longer be present in the throat and the swab will be negative even though the strep bacteria are causing illness in other parts of the body.
- If a rapid strep test is negative but there is still suspicion that the patient has strep throat (or scarlet fever), a throat culture is performed. A throat culture is often performed initially in either case. If a person has a red throat is red and a rash, but the throat culture is negative, this strongly suggests another cause for the illness, (such as adenovirus, roseola, or infectious mononucleosis).
- An ASO titer is a blood test which specifically tests the level of ASO in the blood. ASO is anti-streptolysin O, an antibody to streptolysin O (one of the toxins produced by Streptococcus pyogenes). The ASO level stays high for months following an infection with Streptococcus. The ASO titer is specifically useful since it can detect a recent illness of strep throat, even if the throat infection has already resolved.
- A monospot test is a simple fingerprick blood test which can detect the presence of an antibody seen in infectious mononucleosis. This test is done to make sure that the illness is not due to infectious mononucleosis.
- A complete blood count is a non-specific test. It is done to determine the severity of the infection. If the white blood count is very high, this is suspicious for a worse infection, such as bacteremia or sepsis. If there is suspicion of this, a blood culture is needed. A complete blood count also indicates the level of platelets in the blood. A very high level of platelets (above 1,000,000), may indicate Kawasaki disease instead of scarlet fever.
- Rarely, the bacteria of scarlet fever can spread to the blood, causing bacteremia (infection of the blood). When the infection generalizes throughout the body, sepsis results. Bacteremia and sepsis from scarlet fever is rare, but both are life threatening.
- On very rare occasions, a person may have a silent, or subclinical, case of scarlet fever. The person does not have a sore throat, fever, or rash, but only has peeling of the skin of the hands. This unusual peeling of skin can be confusing, The exact cause may never be determined unless a physician decides to test the individual for the presence of Streptococcus. The throat or an ASO titre may still test positive for strep.
- The diagnosis of scarlet fever can be difficult in African-Americans. The rash usually does not appear scarlet, but can be a faint red or a slightly darker hue than the rest of the skin. The rash may also be entirely absent. The rough "sandpaper-like" rash is easier to detect than the actual rash in many cases.
- A more rare form of scarlet fever is staphylococcal scarlet fever. The signs and symptoms are indistinguishable from scarlet fever caused by Streptococcus except that throat infection is usually absent. Culture of the eyes, nose, or mouth will show Staphylococcus aureus instead of Streptococcus pyogenes. Stronger antibiotics are usually necessary in these cases.
- Scarlet fever is treated with antibiotics. The standard treatment is penicillin, but amoxicillin is usually given instead. Amoxicillin is a derivative of penicillin and tastes better, which makes it easier to give it to children.
- Athough treatment for just five days may be enough to treat the infection, treatment is given for ten days in order to prevent future complications of rheumatic fever and rheumatic heart disease. Ten days of treatment has been proven to prevent these complications.
- If a person is allergic to penicillin, then erythromycin, clindamycin|, or azithromycin is used. Azithromycin (Zithromax) may be used instead of penicillin because fewer doses are needed. However, it has not yet been proven that this azithromycin definitely prevents rheumatic fever or rheumatic heart disease.
- An intramuscular dose of penicillin G as a one-time shot is also effective and may be used instead, particularly where compliance may be difficult. Some parents of children with scarlet fever and some adults may prefer the one-time shot instead of the 10-day course of antibiotics.
- There is no need to retest a person who has been treated for strep throat or scarlet fever, as the cure rate is virtually 100%. If a repeat rapid strep test or the throat culture is still positive, this may indicate a carrier state, in which the individual harbors the bacteria and can pass it along to others. This does not cause problems and is not associated with rheumatic fever or rheumatic heart disease. Treatment with clindamycin to eradicate the Streptococcus definitively may be useful.
- Handwashing is key to the prevention of strep throat. Children with strep throat or scarlet fever should be kept at home, as they are contagious. They remain contagious for about 3-4 hours after antibiotics have reached a steady, effective concentration in their body. This can vary by individual. To ensure the health of other children, children should stay home until at least 24 hours after their first dose of antibiotics.
- Adequate and quick treatment of strep throat can prevent most cases of scarlet fever. However, some cases may present with both scarlet fever and strep throat. In some rare cases, scarlet fever may arise without any recognized symptoms of strep throat. Sometimes, scarlet fever occurs as early as one day after the onset of strep throat.
- Strep throat is very contagious. This illness is spread via saliva, nasal discharge, or through direct contact (touching). It can also spread via objects that someone with the illness has recently touched, such as a doorknob.
- When an individual has scarlet fever, he or she can still be contagious because of the Streptococcus bacteria that is still present in the throat and nose. As such, the bacteria can still be transmitted in the same way as if the individual had strep throat.
- The actual rash of scarlet fever does not have the bacteria in it, although the bacteria may be present on the skin, especially on the hands.
- An individual with scarlet fever does not give another person scarlet fever. Rather, the individual with scarlet fever may transmit the bacteria, Streptococcus pyogenes, which in turn may give someone else strep throat. If that person does not get treatment for the strep throat, then that person may develop scarlet fever.
- When a person acquires the bacteria that causes scarlet fever, it takes about seven days before that person will develop Strep throat. This is called the incubation period. Not every person will develop strep throat, since some people have partial immunity. Scarlet fever may or may not develop afterwards. If it does, scarlet fever usually develops one to seven days later.
- Although most cases are mild, some children and adults can become very sick with scarlet fever. If left untreated for long enough, the infection can spread to the blood and cause bacteremia, pneumonia, or sepsis. Meningitis is rare.
- If left untreated, even if the illness resolves, the individual can be at risk of developing rheumatic fever or rheumatic heart disease. These are autoimmune diseases where the body starts attacking cells of the body that resemble portions of the Streptococcus bacteria.
- Streptococcal glomerulonephritis can occur after a case of strep throat, impetigo, or scarlet fever, usually about 7-14 days afterwards. This disease cannot be prevented with treatment with antibiotics. Fortunately, this disease is usually self-limiting and resolves in about two weeks.
- The incidence of scarlet fever was much higher before the advent of antibiotics. The incidence of scarlet fever varies depending on the incidence of strep throat and on the likelihood of receiving antibiotics. The incidence of strep throat is higher among school age children and lowest among infants. Scarlet fever also follows this trend. This illness is uncommon under 3 years of age. This may be due to lack of exposure, as children generally do not start preschool until after that age. Strep throat, and consequently scarlet fever, is more common in winter months, less common in the summer. The exact reason is not clear. It may be due to the fact that children do not attend school during summer vacation, and may have less exposure to the bacteria as a result.
- Scarlet fever occurs commonly in young adults who have frequent contact with children, such as schoolteachers and pediatricians. Risks are higher in adults who are in close quarters with many other adults, such as in the military, simply because of the ease of spread.
- Scarlet fever is more common in areas where antibiotics are not readily available, such as in Iraq or other war-torn or underdeveloped countries. However, scarlet fever as a complication of strep throat does not occur as often in tropical climates. Instead, impetigo, a skin infection of Streptococcus, is more common.
Other illnesses confused with scarlet fever
- meningococcemia, caused by the bacteria Neisseria meningitidis, is life threatening infection that can be confused with scarlet fever. As mentioned above, a non-blanching rash, purpura (large purple patches), and petechiae (pinpoint red non-blanching dots), all suggest meningococcemia instead of scarlet fever.
- Another illness that presents with a fever, a red rash, and a bright red tongue is Kawasaki disease. Scarlet fever can be differentiated from Kawasaki disease because the latter typically affects a young children under the age of three years. Kawasaki disease is also associated with red eyes and sometimes large lymph nodes in the neck. Changes in the skin of the hands and hand swelling can also occur.
- Infectious mononucleosis, or "mono," also presents with a fever, rash, and a sore throat. The rash is somewhat different, and a test for mono (Monospot test) and strep throat (rapid strep test or throat culture) can distinguish the two. Infectious mononucleosis is also associated with an enlarged spleen.
- Roseola is a viral infection that mainly presents in young children under the age of three. Roseola typically causes a very high fever and a rash that begins after the fever has ended. The rash is also a lacy rash and can also be described as scarlatiniform (like scarlet fever). However, there is no sore throat, and tests for strep are negative.
- Adenovirus infection can sometimes give a child a painful sore throat, a high fever, and a rash. In general, many non-specific viral illnesses can present in children with a fever and a pink or red rash.
- ↑ 1.0 1.1 1.2 Pace B. JAMA patient page. Strep throat. JAMA. 2000 Dec 13;284(22):2964. Abstract | Full Text
- ↑ 2.0 2.1 2.2 Hahn RG, Knox LM, Forman TA. Evaluation of poststreptococcal illness. Am Fam Physician. 2005 May 15;71(10):1949-54. Abstract | Full Text
- ↑ 3.0 3.1 Zwart S, Rovers MM, de Melker RA, Hoes AW. Penicillin for acute sore throat in children: randomised, double blind trial. BMJ. 2003 Dec 6;327(7427):1324. Abstract | Full Text