Scarlet Fever (Scarlatina)

Picture of rash on the arm due to scarlet fever. Source: CDC

Scarlet fever is a bacterial infection caused by group A Streptococcus bacteria. This illness usually occurs in a few people (about 10%) who have strep throat (streptococcal pharyngitis) and occasionally streptococcal skin infections or even wound infections. Scarlet fever is mainly known for its sunburned skin-colored sandpaper-like skin rash that is associated with fever.

Scarlet fever is also known as scarlatina in the older articles; group A Streptococcus (for example, Streptococcus pyogenes) is often shortened to read as "group A strep" or group A beta-hemolytic streptococci (GABHS).

Outbreaks do still occur. England reported a 50-year high number of individuals diagnosed with the disease (over 19,206) in 2016.

Group A beta-hemolytic streptococci (GABHS) bacteria are the cause of scarlet fever. These gram-positive coccus-shaped (elliptically shaped) organisms, while infecting a body site, can produce an erythrogenic (producing red-colored) toxin. This toxin is responsible for causing the sandpaper-like red-colored skin rash.

Researchers have shown that about 80% of children who reach age 10 have developed lifelong protective antibodies against Streptococcus exotoxin. These bacteria can cause other symptoms and/or diseases such as impetigo, skin desquamation, myositis, acute rheumatic fever, and necrotizing fasciitis.

The incubation period for scarlet fever has a fairly wide range from about 12 hours to seven days. Individuals are contagious during this first subclinical or incubation period and the acute illness. The primary strep infection is the contagious aspect. The rash itself is not contagious.

As stated previously, the contagious period for scarlet fever occurs during both the initial subclinical (before the development of symptoms) phase, about 12 hours to seven days after initial contact with the bacteria, and during the acute phase when the person has the rash and fever.

Risk factors for scarlet fever are overcrowded conditions (schools, dormitories, institutional settings). Children 5-15 years of age are the population that is usually seen with scarlet fever, although it can occur in some older children and adults. Scarlet fever is rare in children younger than 2 years old because of maternal antibodies.

Scarlet fever symptoms and signs may include a reddish sore throat, a fever (101 F or above), and a widespread red rash (exanthem) with a sandpaper-like texture, and a tongue that resembles a strawberry (red with small bumps also termed strawberry tongue).

Some patients will have a whitish coating on the tongue or the throat and may have swollen lymph nodes glands, headache, abdominal pain or discomfort resulting in nausea and vomiting, and/or body aches.

The classic description of the rash of scarlet fever has been described as "goose bumps (papule) on sunburned skin" or "boiled-lobster" skin.

In most cases, the patient's history and physical exam will result in a presumptive diagnosis of scarlet fever. For example, the physical exam may reveal Pastia's signs or Thompson's signs where pink or red lines form in skin creases of the armpits and groin. The lines may form before the rash develops and may remain as pigmented lines after desquamation (skin peeling off). However, a healthcare professional may obtain a throat culture or swab (or rarely, swabs from a wound or other sites of infection) to determine if GABHS are present.

Unfortunately, there are many other infections, like measles, that can cause both a skin rash and a fever. Isolation of GABHS usually is enough to confirm the diagnosis of scarlet fever. An infectious disease specialist may be consulted if complications develop. If GABHS is not identified, the symptoms and signs are likely due to another underlying problem.

The treatment for scarlet fever is antibiotics that are effective against GABHS. Usually, about 10 days of oral penicillin medication (for example, amoxicillin) is effective early treatment. Rarely, some patients may need to be treated with a single injection of penicillin G benzathine (Bicillin L-A). This is most commonly indicated for a patient who is unable to retain oral antibiotics. Other effective antibiotics are members of the cephalosporin family (for example, cephalexin [Keflex]).

A recent outbreak in China showed GABHS resistance to the common antibiotics used to treat scarlet fever. Antibiotics may prevent complications of scarlet fever such as rheumatic fever.

Complications from scarlet fever may include kidney disease (termed post-streptococcal glomerulonephritis) and rheumatic fever (an inflammatory disease caused by antibody cross-reactivity that affects the heart, joints, skin, and brain).

• Rheumatic complications can begin about two to three weeks after the initial infection; children between the ages of 6 and 15 are most susceptible to rheumatic fever development.
• Glomerular complications may begin about one to two weeks after throat infection or about three to six weeks after skin infection and usually cause more problems in adults than children.

The prognosis for scarlet fever, when treated appropriately with antibiotics, is usually excellent. Patients recover completely and the skin symptoms progressively decrease over several weeks. Untreated scarlet fever has a worse prognosis and before the use of antibiotics, scarlet fever had a mortality (death) rate of about 15%-20%.

Currently, the mortality rate is less than 1% because of early recognition and early treatment with antibiotics. In general, appropriately diagnosed and treated scarlet fever results in few if any long-term effects. However, if complications develop for whatever reason, problems that include kidney damage, hepatitis, vasculitis, septicemia, congestive heart failure, and even death may occur.

The best way to prevent or lessen the chance of getting a scarlet fever is hand washing. In addition, avoiding communal use of utensils, towels, or other personal items should be avoided. Transmission of the disease is from person to person, usually by droplets, so direct contact with infected individuals should be avoided. Patients who are treated with antibiotics and have had no fever for about 24 hours are considered to be noncontagious. No vaccine is available for humans to prevent scarlet fever.