Fifth disease is a viral infection caused by the human parvovirus B19.Symptoms, when they occur, include mild fever, cough and running nose, which may or may not be followed by a rash. The rash comes and goes, often in response to heat, for several weeks.
Joint pain is common in infected adults, especially women.
Fifth disease is generally a mild illness. However, if a pregnant woman is infected during the first 20 weeks of pregnancy, the infection may be transmitted to the fetus. Rarely, this results in severe anaemia in the fetus. Infection in a patient with a weakened immune system can result in prolonged infection and severe anaemia. Parvovirus B19 infection is diagnosed by a blood test.