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Fifth Disease

Fifth disease, or erythema infectiosum, is a very mild viral illness characterized by a bright red or rosy rash on both cheeks for one to three days ("slapped cheek" appearance), followed by a pink "lacy" or "net-like" rash on the extremities.  The lacy rash appears primarily on the thighs and upper arms.  It can come and go several times over one to three weeks, particularly after warm baths, exercise, and sun exposure.  The rash does not itch.  Your child may have a low-grade fever (less than 101 degrees F), slight runny nose, and sore throat, but he or she may have no other symptoms at all.  Adults may develop joint and muscle aches, but these symptoms are rare in children.

Fifth disease is caused by the human parvovirus B19.  It was so named because it was the fifth of six infectious rashes to be described by physicians.  For historical interest, the six in order are measles, scarlet fever, rubella, "Dukes' disease" (now recognized as variants of existing infectious rashes), erythema infectiosum (fifth disease), and roseola.

The incubation period of fifth disease is usually 4 to 14 days, but may be as long as 21 days.  In some children the illness begins with a brief, mild, nonspecific illness consisting of fever and flu-like symptoms.  The rash then follows 7 to 10 days later, or 2 to 3 weeks after initial acquisition of infection.  Fifth disease is contagious before the appearance of the rash.  Immunity is thought to be lifelong, and more than 90% of elderly people are seropositive for antibody against parvovirus B19.

No treatment is necessary for fifth disease.  By the time the rash appears, your child is not contagious and may return to school.

In the rare instance that a susceptible pregnant woman contracts fifth disease, there is a small possibility that the virus may be harmful to the fetus.  If a pregnant woman is exposed to a child with fifth disease before the child develops the rash, she should contact her obstetrician.

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