A patient had fever and coryza for last 3 days developed a maculopapular erythematous rash with which lasted for 48 hrs and disappeared without leaving behind pigmentation is most commonly due to –

The child is having roseola infantum. It is caused by Human herpes - 6 (HHV-6). The most prominent feature is the abrupt onset of fever often reaching 40.6°C. The fever then ceases abruptly and a characteristic rash may appear. The rashes are maculopapular. Are non pruritic tend to coalesce and disappears in 1-2 days without pigmentation or desquamation. Erythema infectiosum or fifth disease can be easily ruled out because the first sign of illness is the rash no fever. The rashes are masculopapular and they coalesce to given a slapped check appearance. One half of the infected children have some rash remaining for 10 days fine desquamation may be present. In measles, the rashes last for 6-7 days. In typhoid, the rashes appear on the 7th day of illness.