Related concepts:

Exanthem subitum, Human herpesvirus 6, HHV-6, Sixth disease

Introduction to roseola:

After several nights of watching their toddler with a fever, the parents notice a red rash covering his body. Is this a sign of trouble? Or is it good news?

What is roseola?

Roseola is a mild viral illness with a fever followed by a rash. Before the 20th century, children with roseola were lumped in with those with measles or rubella or scarlet fever. It wasn't until 1913 that this specific syndrome was recognized, distinguishing from the others as a benign, self-limited disease occurring almost exclusively in young children.

It is caused by human herpesvirus 6 (HHV-6) or occasionally by human herpesvirus 7 (HHV-7). While the disease has been recognized for almost century, HHV-6 was discovered only in 1986, and HHV-7, in 1990. Roseola is also called roseola infantum (because it occurs mostly in infants), exanthem subitum (meaning “sudden rash”), and sixth disease (because it was the sixth of the similar childhood rash infections to be described). It is one of the classic childhood exanthems.

Who gets roseola?

Almost all cases of roseola occur in children before their third birthdays. The peak age is between 6 and 15 months. Healthy babies are born with protective antibodies from their mothers, but these begin to disappear when the baby is 4 to 6 months old. By 15 months, most babies have protective antibodies that they have made themselves. These will last a lifetime.

Fewer than half of children ever get roseola. Nevertheless, almost all children have had HHV-6 infections by age 3. For the majority, who never get the rash, the HHV-6 infection usually causes a fever, perhaps with other symptoms. It is a common cause of baby’s first fever. HHV-7 follows a similar pattern, but the time sequence is more spread out; most children have become infected before middle school.

What are the symptoms of roseola?

Classic roseola features a high fever (average 103°F) that lasts for 3 to 5 days (worse at night). Most children behave normally, even with the high fevers. In most, the fever ends abruptly, although it can disappear slowly over a day or so. A rash appears within hours of the fever subsiding. The rash is rose-colored, as the name roseola suggests. The rash may be present on the upper arms, legs, and face, but is most prominent on the neck and trunk, where it usually begins. It consists of numerous, small (2- to 5-mm), slightly raised spots that blanch when pressed. The rash does not itch and does not cause blisters. The rash typically lasts for 24 to 48 hours. Sometimes the spots coalesce before the rash disappears. In some children, the rash may be fleeting—gone in minutes or hours.

The most common complication is seizures at the beginning of the high fever in a small number of children.