Roseola symptoms in adults are mild or similar to those of mononucleosis, explains Mayo Clinic. It is more common in those with weak immune systems. Roseola in adults can cause encephalitis and other complications.
Roseola, most common in children under age 2, can infect adults not previously infected. Symptoms include fever and rash and can cause seizures, according to Mayo Clinic.
Adults with weak immune systems, such as the elderly and those undergoing chemotherapy treatments or recent transplants, are more susceptible to contracting the virus, notes Drugs.com. The virus can reactivate in those with compromised immune systems, reports the Annual Review of Medicine.
Roseola has the potential of causing serious complications in adults. Pneumonia or encephalitis can occur, according to Drugs.com. Meningoencephalitis and hepatitis are other complications, notes CHealth.