The rash may be difficult to detect but is more prominent after a hot shower or bath. The rash is often the first sign of infection in children but it is often preceded by the prodromal phase in adults and adolescents. During this period the virus causes a localized infection in the respiratory epithelium. Once this has been established the virus spreads via the blood stream to the regional lymph nodes. The virus then begins to replicate in the nasopharynx and regional lymph nodes.
Viraemia then occurs.