Scarlet fever, also known as scarlatina and scarlatiniform rash, is an infectious disease caused by Streptococcus pyogenes, a Group A streptococcus (GAS). It most commonly affects children and young adolescents between five and 15 years of age. The signs and symptoms include a sore throat, fever, headache, swollen lymph nodes, and a characteristic rash. The face is flushed and the rash is red and blanching. It typically feels like sandpaper and the tongue may be red and bumpy. The rash occurs as a result of capillary damage by exotoxins produced by S. pyogenes. On darker-pigmented skin the rash may be hard to discern. Scarlet fever develops in a small number of people who have strep throat or streptococcal skin infections. The bacteria are usually spread by people coughing or sneezing. It can also be spread when a person touches an object that has the bacteria on it and then touches their mouth or nose. The diagnosis is typically confirmed by culturing swabs of the throat. There is no vaccine for scarlet fever. Prevention is by frequent handwashing, not sharing personal items, and staying away from other people when sick. The disease is treatable with antibiotics, which reduce symptoms and spread, and prevent most complications. Outcomes with scarlet fever are typically good if treated. Long-term complications as a result of scarlet fever include kidney disease, rheumatic fever, and arthritis. 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. This decline is suggested to be due to better living conditions, the introduction of better control measures, or a decline in the virulence of the bacteria. In recent years, there have been signs of antibiotic resistance; there was an outbreak in Hong Kong in 2011 and in the UK in 2014, and occurrence of the disease rose by 68% in the UK between 2014 and 2018. Research published in October 2020 showed that infection of the bacterium by three viruses has led to more virulent strains of the bacterium.
Signs and symptoms Scarlet fever typically presents with a sudden onset of sore throat, fever, and malaise. Headache, nausea, vomiting and abdominal pain may also be present. Scarlet fever usually follows from a group A streptococcal infection that involves a strep throat, such as streptococcal tonsillitis or more usually streptococcal pharyngitis. Often these can present together, known as pharyngotonsillitis. The signs and symptoms are therefore those of a strep throat but these are followed by the inclusion of the characteristic widespread rash. The rash usually appears one to two days later, but may appear before or up to seven days following feeling ill. It generally hurts to swallow. 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. Cough, hoarseness, runny nose, diarrhea, and conjunctivitis are typically absent in scarlet fever; such symptoms indicate what is more likely a viral infection.
Mouth and throat
Strep throat is usually associated with fatigue and a fever of over 39 °C (102.2 °F). The tonsils may appear red and enlarged and are typically covered in exudate. The throat may be red with small red spots on the roof of the mouth. The uvula can look red and swollen. 30% to 60% of cases have associated enlarged and tender lymph nodes in the neck. During the first two days of illness the tongue may have a whitish coating from which red swollen papillae protrude, giving the appearance of a "white strawberry tongue". After four to five days when the white coating sheds it becomes a "red strawberry tongue". The symptomatic appearance of the tongue is part of the rash that is characteristic of scarlet fever.
Rash
The characteristic rash has been denoted as "scarlatiniform", and it appears as a diffuse redness of the skin with small bumps resembling goose bumps. It typically appears as small flat spots on the neck or torso before developing into small bumps that spread to the arms and legs. It tends to feel rough like sandpaper. The cheeks might look flushed with a pale area around the mouth. The scarlet fever rash generally looks red on white and pale skin, and might be difficult to see on brown or black skin, in whom the bumps are typically larger, the skin looks like sandpaper, and the paleness around the mouth is less obvious. The rash does not appear on the palms and soles. The reddened skin blanches when pressure is applied to it. The skin may feel itchy, but is not painful. A more intense redness on the inside of skin folds and creases might be noticed. These are lines of petechiae, appearing as pink/red areas located in arm pits and elbow pits. It takes around a week for the main rash to disappear. This may be followed by several weeks of peeling of the skin of typically fingers and toes. The desquamation process usually begins on the face and progresses downward on the body. Sometimes, this peeling is the only sign that scarlet fever occurred. If the case of scarlet fever is uncomplicated, recovery from the fever and clinical symptoms, other than the process of desquamation, occurs in 5–10 days. After the desquamation, the skin will be left with a sunburned appearance.
Variable presentations Children younger than five years old may have atypical presentations and many of the common signs and symptoms may be missing or different. Children younger than 3 years old can present with nasal congestion and a lower grade fever. Infants may present with symptoms of increased irritability and decreased appetite.
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