Background: Infection with human herpes virus 6 (HHV-6) occurs in infancy or early childhood. Primary HHV-6 infection accounts for 10-20% of all febrile illnesses in infants and children less than 3 years of age seen in pediatric emergency departments. Serious complications have been described such as meningitis, encephalitis, hepatitis (including neonatal hepatitis), disseminated infection and hemophagocytic syndrome. At least one case of verified transmission from mother to foetus has been described. HHV-6 is closely related to CMV, which is transmitted from mother to infant in 0.5-2.0 of all pregnancies, most often as a result of reactivation of the virus.

Subjects: Blood samples were collected from 107 newborn infants(cord blood) and their mothers (venous puncture). Blood samples from 20 healthy adults were used as controls.

Methods: All blood samples were collected in EDTA tubes. Cells and plasma were separated by Ficoll-Paque separation. DNA from 200 000 leucocytes were analysed in a variant-specific HHV-6 PCR. The PCR product from the HHV-6 DNA positive pairs were used for sequensing.

Results: HHV-6 DNA could be detected in 6/107 (5.6%) of the cord blood samples. So far 5 of these 6 infant/mother pairs have been analysed by sequensing, showing identical sequenses in the gene examined for all 5 pairs. HHV-6 DNA was found in leukocytes from 56/107 (52%) of the mothers at delivery, compared to 1/20 (5%) in the control group.

The 6 newborn infants with positive HHV-6 PCR in cord blood had all a normal neonatal period except for one infant who was treated for an uncomplicated hyperbilirubinemia.

Conclusion:

  1. 1

    HHV-6 can be transmitted from mother to infant during pregnancy and/or delivery.

  2. 2

    HHV-6 tends to become reactivated during pregnancy.