Fifth disease is also referred to as erythema infectiosum (meaning infectious redness) and as slapped cheek syndrome.
Until recently, its cause was unknown: it is now known to be caused by Parvovirus B19, discovered in 1975.
Patients are usually no longer infectious once the characteristic rash of this disease has appeared. Any age may be affected although it is most common in children aged six to ten years. By the time adulthood is reached about half the population will have become immune following infection at some time in their past. Outbreaks can arise especially in nurseries and schools.
A significant increase in the number of cases is seen every three to four years; the last epidemic year was 1998.
The disease is usually mild, but it does have the ability to cause some serious problems: it is associated with spontaneous abortion in pregnant women, and with aplastic crisis in persons with chronic hemolytic anemia.
The name fifth disease stems from the fact that when diseases causing childhood rashes were enumerated, it was the fifth listed. The list of such diseases is:
- measles, rubeola, 14-day measles
- scarlet fever, scarlatina
- rubella, German measles, 3-day measles
- Duke's disease (caused by various viruses including coxsackievirus, enterovirus, or echovirus)
- fifth disease (erythema infectiosum, slapped cheek syndrome), caused by Parvovirus B19
- sixth disease (exanthem subitum, roseola infantum, rose rash of infants, baby measles)\n
