For the first week or two after becoming infected, the virus will multiply in the body, usually causing no symptoms. Children may appear irritable during this time. After this period of incubation, symptoms begin to appear. Children will develop a sudden high fever as high as 39°C to 40°C (102.2°F to 104°F) lasting 3 to 5 days. Despite the fever, children are usually alert and do not appear ill. However, some children may also have a mild sore throat, runny nose, cough, swollen glands, and mild diarrhea either before or during the fever. Some children also experience fatigue, swollen eyelids, and a decreased appetite.
The fever will usually subside by the fourth day, but this is followed by a characteristic faint, rosy-pink widespread rash that may develop. Small, flat, discoloured spots on the skin with tiny raised bumps (2 mm to 5 mm in diameter) first appear on the trunk of the body. This rash may then spread to the neck and legs, but rarely will it involve the face. This rash is neither itchy nor pus-forming and tends to whiten when pressure is applied to the reddened area. Typically, the rash will clear within a few hours, but may last up to 2 days. For some people, the rash may even be mild enough to go unnoticed or may not even appear.
The sudden onset of a high fever may cause convulsions or seizures called febrile seizures. This is more common in infants and young children between the ages of 6 months to 3 years and occurs in 6% to15% of children. If your child does experience a febrile seizure, get immediate medical attention. Fortunately, febrile seizures are usually very short and are very rarely harmful. Aside from febrile seizures, complications in children are rare.
Roseola in adults can cause severe complications including meningoencephalitis, an infection of the brain tissue and its surrounding layers, or hepatitis, an inflammation of the liver.