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Erythema Infectiosum +er-u-!thE-mu-in-+fek-shE-!O-sum

by Mary T. Caserta, MD

Erythema infectiosum (fifth disease, parvovirus B19 infection) is a contagious viral infection that causes a blotchy or raised red rash with mild illness.

  • Erythema infectiosum is caused by a virus.

  • Symptoms include a mild fever; slapped-cheek red rash on the face; and a lacy rash on the arms, legs, and trunk.

  • The diagnosis is based on the characteristic rash.

  • Treatment aims to relieve symptoms.

Erythema infectiosum is caused by human parvovirus B19 and occurs most often during the spring months, often in geographically limited outbreaks among children and adolescents. Infection is spread mainly by breathing in small droplets that have been breathed out by an infected person. The infection can also be transmitted from mother to fetus during pregnancy, rarely resulting in stillbirth or severe anemia and excess fluid and swelling (edema) in the fetus (hydrops fetalis).

Symptoms begin about 4 to 14 days after infection but many children have none. However, some have a low fever and feel mildly ill for a few days. Seven to 10 days later, children develop red cheeks that often look like they have been slapped as well as a rash, especially on the arms, legs, and trunk but not usually on the palms or soles. The rash can be itchy and consists of raised, blotchy red areas and lacy patterns, particularly on areas of the arms not covered by clothing, because the rash may be worsened by exposure to sunlight.

The rash usually lasts 5 to 10 days. Over the next several weeks, the rash may temporarily reappear in response to sunlight, exercise, heat, fever, or emotional stress. In adolescents, mild joint pain and swelling may remain or come and go for weeks to months.

Erythema infectiosum can also manifest in a different way, particularly in children with sickle cell disease or in children with immunodeficiency diseases, such as acquired immunodeficiency syndrome (AIDS). The virus can affect the bone marrow and cause severe anemia.

A doctor bases the diagnosis on the characteristic appearance of the rash. Blood tests can help identify the virus, although these are rarely done. Treatment is aimed at relieving the symptoms.