Merck Manual

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Erythema Infectiosum

(Fifth Disease; Parvovirus B19 Infection)


Brenda L. Tesini

, MD, University of Rochester School of Medicine and Dentistry

Reviewed/Revised Jul 2021 | Modified Sep 2022
Topic Resources
  • 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 is aimed at relieving symptoms.

Erythema infectiosum, often referred to as fifth disease, is caused by human parvovirus B19 and occurs most often during the spring months, often in geographically limited outbreaks among children, particularly school age children. Infection is spread mainly by breathing in small droplets that have been breathed out by an infected person, so infection tends to spread within a household. The infection can also be transmitted from mother to fetus during pregnancy, rarely resulting in stillbirth Stillbirth Stillbirth is death of a fetus after 20 weeks of pregnancy. Stillbirth may result from a problem in the woman, placenta, or fetus. Doctors do blood tests to try to identify the cause of a stillbirth... read more or severe anemia and excess fluid and swelling (edema) in the fetus (hydrops fetalis).

Symptoms of Erythema Infectiosum

Erythema infectiosum symptoms begin about 4 to 14 days after infection. Many children have no symptoms. However, some children have a low fever and feel mildly ill with a headache and a runny nose for a few days. Several 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 and the entire illness usually last 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.

Diagnosis of Erythema Infectiosum

  • A doctor's evaluation

A doctor bases the diagnosis of erythema infectiosum on the characteristic appearance of the rash. Blood tests can help identify the virus, but these are rarely done except in children who have a known blood disorder or an impaired immune system.

Treatment of Erythema Infectiosum

  • Relief of symptoms

Erythema infectiosum goes away on its own so treatment is aimed at relieving the symptoms. Children may be given nonsteroidal anti-inflammatory drugs (NSAIDs) to relieve fever, achiness, headache, and joint pain and other drugs to relieve itching if it is severe.

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