Fifth disease, or erythema infectiosum, is a mildly to moderately contagious viral infection common among school-age children, particularly in the winter and spring.
Though it can resemble other childhood rashes, such as rubella or scarlet fever, fifth disease usually begins with the distinctive, sudden appearance of bright red cheeks that look as though the child has been slapped. The disease is rare in infants and adults.
Fifth disease got its name many years ago when it was the fifth on a list of the six recognized childhood rash-forming illnesses; the others include rubella, measles, scarlet fever, chickenpox, and roseola infantum. It also is called slapped-cheek disease because of the characteristic initial appearance in children.
Fifth disease is usually mild. It is spread by respiratory droplets that enter the air when an infected person coughs or sneezes, or through blood. It poses little risk to healthy children and adults, with a couple of exceptions: pregnant women and people with certain types of chronic anemia. If a pregnant woman is infected in the first half of her pregnancy, there is a small risk of severe anemia in the fetus and a 10% risk of miscarriage.
Fifth disease is caused by parvovirus B19 and is spread by respiratory secretions from an infected person. By the time the rash appears, children are no longer contagious and may attend school or day care. The incubation period (the period between infection and signs or symptoms of illness) is usually four to 14 days, but can be as long as 21 days.
Adults who work with young children -- such as child-care providers, teachers, and those in health care fields -- are most likely to be exposed.
SOURCES: American Academy of Pediatrics. 2003 Red Book Report on the Committee of Infectious Diseases (Amerian Academy of Pediatrics Committee on Infections Diseases//Report of the Committee on Infections Diseases)