Fifth disease

Erythema infectiosum or fifth disease is one of several possible manifestations of infection by erythrovirus, previously called parvovirus B19. The disease is also referred to as slapped cheek syndrome, slapcheek, slap face or slapped face. In Japan the disease is called "apple sickness" or ringo-byou (りんご病）in reference to the symptom of facial redness. In Hungary it is called "butterfly pox" as the red cheeks look like the wings of a butterfly.

Symptoms
Fifth disease starts with a low-grade fever, headache, and cold-like symptoms, such as a runny or stuffy nose. These symptoms pass, then a few days later the rash appears. The bright red rash most commonly appears in the face, particularly the cheeks. This is a defining symptom of the infection in children (hence the name "slapped cheek disease"). Occasionally the rash will extend over the bridge of the nose or around the mouth. In addition to red cheeks, children often develop a red, lacy rash on the rest of the body, with the upper arms, torso, and legs being the most common locations. The rash typically lasts a couple of days and may itch; some cases have been known to last for several weeks. Patients are usually no longer infectious once the rash has appeared.

Teenagers and adults may present with a self-limited arthritis. It manifests in painful swelling of the joints that feels similar to arthritis. Older children and adults with fifth disease may have difficulty in walking and in bending joints such as wrists, knees, ankles, fingers, and shoulders.

The disease is usually mild, but in certain risk groups it can have serious consequences:
 * In pregnant women, infection in the first trimester has been linked to hydrops fetalis, causing spontaneous miscarriage.
 * In people with sickle-cell disease or other forms of chronic hemolytic anemia such as hereditary spherocytosis, infection can precipitate an aplastic crisis.
 * It should also be noted that those who are immuno-compromised (HIV/AIDS, Chemotherapy) may be at risk for complications if exposed.

Transmission
Fifth disease is transmitted primarily by respiratory secretions (saliva, mucus, etc.) but can also be spread by contact with infected blood. The incubation period (the time between the initial infection and the onset of symptoms) is usually between 4 and 21 days. Individuals with fifth disease are most infectious before the onset of symptoms. Typically, school children, day-care workers, teachers and mothers are most likely to be exposed to the virus. When symptoms are evident, there is little risk of transmission; therefore, symptomatic individuals need not be isolated.

Epidemiology
Any age may be affected although it is most common in children aged five to fifteen years. By the time adulthood is reached about half the population will have become immune following infection at some time in their past. Outbreaks can arise especially in nursery schools, preschools, and elementary schools.

History
The name "fifth disease" is not typically capitalized, since the name derives from its historical classification as the fifth of the classical childhood skin rashes or exanthems. Their classification is as follows:
 * 1) Measles
 * 2) Scarlet fever
 * 3) Rubella
 * 4) Dukes' disease
 * 5) Fifth disease (erythema infectiosum)
 * 6) Roseola

It was first described by Robert Willan in 1799 as "Rubeola, sine catarrho". It was better defined by Anton Tschamer in 1889 as a rubella variant ("Ortliche Rotheln"), identified as a distinct condition in 1896 by T. Escherich, and given the name "erythema infectiosum" in 1899.

Treatment
Treatment is supportive as the infection is frequently self-limiting. Anti-pyrogens (i.e., fever reducers) are commonly used. The rash is painless and non-pruritic (not itchy), requiring no specific therapy.