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Transmission of human herpesvirus 7 through multigenerational families in the same household.

BACKGROUND
Human herpesvirus 7 (HHV-7) closely resembles HHV-6 and to a lesser degree cytomegalovirus. HHV-7 infection is usually acquired during early childhood. Primary infection can cause a roseola-like illness but in most cases it is only mildly symptomatic. The majority of adults are seropositive and in contrast to HHV-6 and cytomegalovirus infection, they continue to secrete the virus in their saliva for many years. The mode of intrafamilial transmission of this virus is not well-understood.


METHODS
Saliva samples for virus isolation and DNA restriction analysis were obtained from all 47 members of 6 Japanese families, including 4 families with 3 generations living in the same household.


RESULTS
HHV-7 was isolated from 43 of 47 saliva samples collected from children and adult members of the 6 families (91.5%). In one family the restriction patterns of the maternal grandmother, the mother and the children were similar, and the patterns of the paternal grandmother and the father were similar. In another family the patterns of the father and 5 of 6 children were similar, and those of the mother and the other child were similar. Altogether similar HHV-7 restriction profiles with his or her mother were found in 48% of offspring, and similar profiles with his or her father were found in 28% of offspring.


CONCLUSIONS
The results strongly suggested horizontal transmission of HHV-7 from grandparents to parents to children through close contact within a household. Either parent could transmit HHV-7 to the children.