Is Human Herpesvirus-8 Transmitted by Transfusion?

Studies of human herpesvirus-8 (HHV-8) transmission through transfusion have produced contradictory results. In North America—a region with a low prevalence of HHV-8 infection—3 studies that tested specimens from linked positive-donor/negative-recipient pairs collected before the introduction of white blood cell (WBC) reduction and the extension of red blood cell (RBC) storage found no case of transmission of HHV-8 to 151 transfusion recipients who were HHV-8–seronegative before the transfusion and received components from HHV-8–seropositive donors. In Uganda, a prospective cohort study of pediatric transfusion recipients observed a small (≤2.8%/U) increase in the risk of HHV-8 seroconversion over 6 months of follow-up among children who received HHV-8–seropositive (compared with seronegative) transfusion. This excess risk may be due either to the transfusion of non-WBC–reduced and fresh RBC units from donors experiencing a high incidence of HHV-8 primary infection or virus reactivation, or to the acquisition of HHV-8 from other background sources in such a high-prevalence geographic area. Although no adequate explanation exists for the difference, transmission routes of HHV-8 differ strikingly between high- and low-prevalence areas, so that findings of studies from Africa should not be generalized to the situation in North America. Even if fresh and non-WBC–reduced units collected from donors with unusually high viremia were capable of transmitting HHV-8 to transfusion recipients in the United States, such a transmission risk would represent a rare event that does not warrant implementation of safety measures specifically for its prevention.