Exanthem subitum (roseola infantum, three-day fever) is quite a common disease in infancy.
The child has a high temperature for 2 to 4 days without noticeable catarrhal symptoms.
With the decrease in temperature an exanthem appears on the whole body. The rash
is macular and of morbilliform (=like measles) or rubelliform (=like rubella) appearance.
Although the temperature stays low there may still be irritation because of the itchy rash.
Febrile seizures are not uncommon and make the elimination of bacterial meningitis necessary. Urinary tract infections, too, have to be eliminated through a urine test. Exanthem subitum has no definite incubation period. It is usually 3-7 days but can take up to 17 days. The risk of contagion is not great, but in rare cases several members of a family can be infected. The resulting immunity is probably life-long, but the disease can reappear if the immune system is weakened.
Children can repeatedly fall ill with a high temperature and following rash. This is because every viral disease can be accompanied by a skin rash, the three-day fever typically at the end of the period of high temperature, other viral diseases at the same time as the fever (e.g. measles).
Some viral exanthems seem not to have been preceded by any signs of an illness. But on closer enquiry it emerges that the child has been off its food during the previous days, has been more clingy or fretful than usual. The appearance of the rash then makes it clear that the child has gone through a viral infection.Differential diagnosis: