Two herpes virus strains cause the childhood disease roseola. Roseola frequently manifests as a fever and a rash on the neck and trunk. It will probably take 5–15 days for your child to show symptoms of illness if they are exposed to someone who has roseola and contracts the virus. The virus can spread by saliva or other respiratory droplets when an infected child coughs, sneezes, or talks, making it contagious even before the rash appears.