The rapid diagnosis and clinical features of human herpesvirus 6.

Since human herpesvirus 6 (HHV6) was first linked with exanthem subitum in 1988 there has been increasing evidence that the morbidity associated with acute HHV6 infection may be more significant and variable. However, the clinical appreciation of HHV6 infection has been hampered by the lack of rapid and clinically useful diagnostic methods. In this prospective study of hospitalized febrile children under 3 years of age we compared three rapid viral diagnostic methods, (polymerase chain reaction assay (PCR), IgM serology and direct antigen detection), with conventional serology on paired serum samples. In addition, we documented the range of clinical features associated with acute HHV6 infection. Of 67 children recruited, 11 (16%) had evidence of acute HHV6 infection: six had detectable, specific, IgM; four were PCR positive; and one was PCR positive with IgM. Direct antigen testing on batched frozen samples detected no infections. Apart from high fever (median peak 38.5 degrees C), common features were non-specific. Two children had febrile convulsions and only one child had a non-specific rash. We conclude that rapid microbiological diagnosis at present requires two tests (IgM and PCR). HHV6 is a common cause of febrile illness in hospitalized infants with no rash and should be considered in their diagnosis.