The association between acute human herpesvirus-6 (HHV-6) infection and first febrile convulsions was investigated prospectively in 42 children evaluated by virologic and serologic methods at the North Shore University Hospital-Cornell University Medical College, Manhasset, New York. Primary HHV-6 infection was documented by viral culture in 8 (19%), and fourfold rises in HHV-6 titer were present in 9 (26%) of 34 children whose blood was analyzed for acute and convalescent HHV-6 titers. The majority (10 of 11) HHV-6 cases were less than 24 months of age, and 3/11 had roseola. Viral isolation in CSF, attempted in 29, including 7 with evidence of HHV-6 illness, was negative. 
COMMENT. Acute HHV-6 infection is a significant factor in the etiology of fever and convulsions in young children. Seizures associated with exanthem subitum and HHV-6 infection are not always simple in type, however. They are occasionally prolonged and complex and a manifestation of encephalitis or encephalopathy. See Progress in Pediatric Neurology II, 1994, Chicago, PNB Publishers, for a report and comment on HHV-6 infection, exanthem subitum, and encephalitis/encephalopathy. HHV-6 virus DNA was detected in the cerebrospinal fluid of 6 infants with exanthem subitum, 3 having a pleocytosis and elevated protein in the CSF.