It is thought that the most likely route for transmission is breast feeding as well as aerosol transmission and saliva from mothers to babies. Breast feeding though, is unlikely to play the major role in the transmission, as babies who are not breast fed were shown to have acquired antibody rapidly as well. Sexual spread is not thought to be a route of transmission of the virus. It is the causative agent for roseala Infantum. Most cases occur in infants between the ages of 4 months and two years, with over half the cases occurring in the second 6 months of life.
Secondary cases are rare in clinical practice.
A spiking fever develops over a period of 2 days followed by a mild rash. The fever is high enough to cause febrile convulsions. There are reports that the virus can cause encephalitic symptoms, possibly due to prolonged seizure. It is now also associated with a glandular fever like illness. It is also associated with hepatitis part of the IM syndrome.