..Fifth's disease

Years ago someone decided that it would make more sense to categorize the rash causing infectious diseases of children by number rather than name.  And so, as the story goes, they attempted to rename measles, chicken pox, German measles, erythema infectiosum, and several other rashes that have been forgotten as "First Disease", "Second Disease", etc.  Guess which one stuck?  Of course, the one that you can't pronounce otherwise.

Erythema infectiosum, also known as fifth disease and "slapped-cheek" disease, most commonly affects children between the ages of four and 10 years and is the most recognizable illness associated with parvovirus B19 infection. Although the clinical features of erythema infectiosum have been recognized for almost two centuries, not until the early 1980s was the link between this exanthem and parvovirus B19 established. It is now known that parvovirus B19 is the only etiologic agent of erythema infectiosum.¹⁷

The classic course of erythema infectiosum can be divided into three distinct stages (Table 2). The first stage, occurring after an incubation period of four to 14 days, consists of a mild prodromal illness characterized by low-grade fever, headache and gastrointestinal symptoms. This stage, which often is unrecognized, corresponds with the period of viremia and the period of contagion.

The second stage of the illness, occurring three to seven days after the prodrome, is characterized by the appearance of a bright erythematous facial exanthem (Figure 1). Because this exanthem most commonly involves the malar eminences and spares the nasal bridge and perioral areas, the characteristic "slapped-cheek" appearance becomes evident. This stage is seen more commonly in children than in adults, and the exanthem may become more marked with exposure to sunlight.

The third stage of the illness occurs one to four days after the appearance of the facial exanthem and is characterized by the appearance of a lacy, erythematous, maculopapular exanthem on the trunk and extremities (Figure 2). This eruption may be pruritic and often is evanescent, recurring over one to three weeks. Because the appearance of the exanthem corresponds with the development of antibody, patients with the rash of erythema infectiosum are no longer contagious.

"Parvovirus B19 Infections", by Sabella and Goldfarb, American Family Physician, October 1, 1999 

Which is a long way of saying that Fifth's Disease has been recognized for a very long time.  While it is epidemic certain times of year, it's course is benign and uneventful.

for further reading:

• article 1 - from American Family Physician

• article 2 - from Dr. Koop

• article 3 - from CDC

  • infection during pregnancy - even though this says "Usually, there is no serious complication for a pregnant woman or her baby", I think that this still overstates the danger somewhat and should have said, "rarely, ..."