Objective .?To elucidate clinical features of patients with primary human herpesvirus 7 (HHV-7) infection and serologic and virologic findings between HHV-7 and human herpesvirus 6 (HHV-6).Materials and Methods .?During a 19-month observation period, 71 infants and children (35 boys and 36 girls with a mean age of 14.5 months [range, 1 month to 48 months]) who had acute febrile respiratory illness with or without skin rash were examined clinically and virologically. Heparinized blood samples were used for isolation of HHV-6 and HHV-7 and detection of both virus DNA sequences by a nested polymerase chain reaction amplification. Both virus antibody activities were measured by an indirect immunofluorescent assay.Results .?HHV-7 infection was observed in 15 (6 boys and 9 girls with a mean age of 12.9 months [range, 7 months to 27 months]), 1 of 10 with upper respiratory infection and 14 (28%) of 50 with febrile exanthem, whereas HHV-6 infection was in 22 (44%) of the 50. Fever (37.5°C) was observed in all 15, with an average maximum body temperature of 38.7°C (range, 37.6°C to 39.8°C), which persisted for 2.9 days (range, 1 to 5 days). Papular, macular, or maculopapular rash was observed in 14 (93%) of the 15, which appeared on day 2.9 of fever (range, days 2 to 5) on the face, trunk, and extremities and persisted for 2.7 days (range, 1 to 5 days). A convulsive seizure that persisted for a few minutes developed in 1 patient on the first day of elevation of fever. HHV-6 antibody was demonstrated in 13 (87%), and a simultaneous significant increase to HHV-6 antibody titers was observed in 8 (53%) of the 15 during primary HHV-7 infection. HHV-7 and HHV-6 DNAs were almost always detected in mononuclear cells (MNCs) during acute and convalescent phases, whereas HHV-7 DNA was positive in some plasma samples obtained during the acute phase of the disease.Conclusions .?Primary HHV-7 infection occurred somewhat later than HHV-6, which was confirmed by the isolation of HHV-7 from blood and/or seroconversion to the virus. Clinical features of a virologically confirmed patient with primary HHV-7 infection were comparable with those of primary HHV-6 infection. Preexisting HHV-6 antibody increased significantly in the half of patients with primary HHV-7 infection. HHV-7 DNA was detected in peripheral blood MNCs and plasma in the acute phase and persisted in MNCs thereafter. human herpesvirus 7, human herpesvirus 6, exanthem subitum, roseola infantum, polymerase chain reaction.
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