Primary human herpesvirus‐6 infection is frequently overlooked as a cause of febrile fits in young children

Abstract

Sera from 248 children aged 30–179 weeks were tested retrospectively for human herpesvirus‐6 (HHV‐6) IgG antibody avidity. Twenty‐five children presented with febrile fits, in one case with a rash, exanthem subitum resulting from primary HHV‐6 infection was diagnosed at the time, but in the others HHV‐6 was not considered in the differential diagnosis even though two patients had a rash. In fact, five of the 25 patients experienced primary infection as shown by low avidity HHV‐6 antibody. Although nine other of these patients were seronegative in the acute phase of the illness, and unfortunately convalescent sera were not available to confirm primary HHV‐6 infection, seronegativity was clearly a risk factor for febrile fits (P = 0.03, odds ratio 3.14 for all children; P = 0.002, odds ratio 7.20 for children aged 70–179 weeks), and primary HHV‐6 infection was a very likely diagnosis. The remaining 11 children had high avidity antibody, so HHV‐6 was excluded as a cause of their febrile fits. HHV‐6 may frequently be a cause of febrile fits, often without the typical rash of exanthem subitum, and this diagnosis is often overlooked by clinicians.