Human herpesvirus 6 (HHV6) virus is spread through saliva and possibly by genital secretions. HHV6 infection in infants results in exanthema subitum (roseola) and is the most common cause of fever-induced seizures. Infection in adults is seen primarily in immunocompromised hosts undergone organ transplants or in those with HIV infection. Evidence of past HHV6 infections is found in most people, but initial infection usually occurs within the first 2 years of life.

Human herpesvirus 7 (HHV7) is very similar to that of HHV6. Both HHV7 and HHV6 appear to cause ubiquitous infections in early childhood, yet primary HHV7 infections are rarely recognized. HHV7 infection is associated with a number of other symptoms, including acute febrile respiratory disease, fever, rash, vomiting, diarrhea, low lymphocyte counts and febrile seizures though most often no symptoms present at all.