Human herpesvirus-6 (HHV-6) infection, incidence, course, complications, and its potential for persistence or reactivation, was studied in infants and children under 3 years of age seen in the ER over a three-year period at the University of Rochester School of Medicine, NY. Of 1653 presenting with acute febrile illnesses, 160 (10%) had primary HHV-6 infection, documented by viremia and seroconversion, and of these, 21 (13%) had seizures, many appearing late and prolonged or recurrent. The risk of seizures among children 12-18 months old with HHV-6 infection was 29%. HHV-6 infections accounted for one third of all first-time febrile seizures in children up to 2 years of age. Among 1394 children under 2 years with fever not due to HHV-6, seizures occurred in 9%. The HHV-6 genome persisted in blood mononuclear cells in 66% of 56 children followed for 1 to 2 years after primary infection. Reactivation was suggested by subsequent increases in antibody titers and PCR in 16% and 6%, respectively. Presence of HHV-6 genome in 29% of 41 healthy neonates’ mononuclear cells indicates intrauterine or perinatal transmission of the virus. Among children with HHV-6 illness, roseola was diagnosed in 17%. 
COMMENT. Human herpesvirus-6 infection in relation to febrile seizures is discussed in two previous issues of Ped Neur Briefs (April 1992; June 1993). These reports concerned a total of 23 infants with CNS complications of roseola (exanthem subitum) caused by HHV-6. The seizures were often prolonged, some were focal, and the csf showed a pleocytosis in 5. The present report and findings suggest that HHV-6 infection may account for a much larger percentage of seizures with fever in children than previously recognized. In addition to roseola, HHV-6 infection presented as otitis or fever of undetermined cause. Febrile children with HHV-6 had significantly higher temperatures than HHV-negative children, the factor generally proposed to explain the frequency of seizures with roseola. The study corroborates the suggestion that seizures with roseola, HHV-6, and fever are not always simple in type. They are frequently prolonged, recurrent, and complex, and sometimes a manifestation of encephalitis or encephalopathy . These findings further weaken the hypothesis of the so-called simple febrile seizure as a distinct disease entity.
For abstracts from the 16th annual conference on febrile convulsions held in Tokyo, Dec 18, 1993, see Fukuyama Y . Papers included neurochemical aspects, EEG studies, and clinical, epidemiological, and treatment reports. The reputed safety and effectiveness of intermittent oral diazepam (0.4 mg/kg, 3 doses) at times of fever for prevention of recurrence of febrile seizures was supported in 23 children treated at Shimane Medical University and Central Hospital, Japan.