Epidemiological data for HHV-6 and HHV-8 in blood donor in Greece is poor. HHV-8 is the etiological agent for Kaposi sarcoma, Castelmann’ disease and primaty effusion lymphoma. Kaposi Sarcoma unrelated to HIV infection is more common in countries of Mediterranean “basin” such as Greece and Italy than in Northern Europe and the USA .
The seroprevalence of HHV-8 in blood donors in Southern Europe ranges from 4.5% (9/200) in Spain Basque country to 20% and 25% in Sicily and Sardinia respectively. Interestingly, a seroprevalence of 2.4% was reported recently in Eastern Sicily . However, the seroprevelance in blood donors in the U.K. (2.7%) and the United States (1.4%) is significantly lower [5, 6].
Since HHV-8 modes of transmission are elusive and the HHV-8 transmission through blood transfusion differs in endemic and non endemic areas, assessing HHV-8 seroprevalence among blood donors in Greece would help us identify the putative danger of transfusion related HHV-8 transmission in Greece. We have also previously found that 48% of the HIV-1-positive and 56% of the HEPS subjects in Greece tested positive for anti-HHV-8 antibodies, a prevalence which is higher than that reported in other countries of Western Europe . All the above mentioned data triggered the study of the seroprevalence of HHV-8 in healthy blood donors in Greece. It has been previously reported that the prevalence of HHV-8 in the general population in Greece is 7.6% and that the seropositivity for HHV-8 was associated with a history of endoscopic procedures and HBsAg positivity . Nevertheless, we found no blood donor tested positive for HHV-8 IgG antibodies. We have used an ELISA with similar sensitivity detecting HHV-8 IgG antibodies  with the previous study and thus the discrepancy between the two studies could be attributed either to the relatively small size of our study or the differences between the general population and the blood donors population. We cannot overlook the fact that with the help of the donor screening questionnaire we practically exclude candidate donors with risk factors for HHV-8 transmission. Endoscopic procedures in the 6 months preceding blood donation, HBsAg seropositivity, and high-risk sexual behaviour are exclusion criteria for a blood donor.
In terms of HHV-6, the seroprevalence of HHV-6 in blood donors in Greece is unknown. Existing literature deals only with the detection of HHV-6 in the sera or tissue from patients with certain disease entities [10–14]. We detected HHV-6 IgG antibodies in 78.75% of blood donors, a seroprevalence similar to the one reported from other countries. Furthermore, the distribution between sexes and among age groups confirms the fact that infection with HHV-6 occurs early in life and that the IgG antibodies persist for a long time.
Blood transfusion–related transmission of herpesviruses from chronically infected donors to previously uninfected or immunocompromised recipients has been a subject of investigation for several years. The possibility of transfusion-related transmission of herpesviruses from healthy adult blood donors is moderately high for HHV-6, while it seems to be very low for HHV-8 .
A number of studies have shown that even in blood donors, who tested positive for HHV-8, HHV-8 DNA was rarely detected. Moreover, it has been suggested that leukoreduction could efficiently remove HHV-8 from blood donations, although some authors argue that this is true only in terms of the viral cellular counterpart. Cell-free HHV-8 was still present in a ranging percentage in 42% of subjects after filtration, as 1% to 20% of the total virus was not removed . Furthermore, it seems that transfusion with fresh blood from HHV-8 positive blood donors can be associated with an increased risk of death . But the fact, that no blood donor was positive for anti-HHV-8 IgG antibodies indicates that the risk for HHV-8 transmission with transfusion in Greece, if any, is negligible and does not warrant broad testing for HHV-8.
Regarding HHV-6 transmission with transfusion, the natural course of transfused WBCs carrying latent integrated HHV-6 in a immunocompetent recipient is the elimination of infected donor cells. However, in immunodeficient patients, especially those who receive stem cell transplants, there is an existing possibility that the integrated virus in the transplanted hematopoietic cells can be reactivated and lead to acute infection .
Although HHV-6 seropositivity reported from several studies is high, HHV-6 DNA is detected only in a small proportion of seropositive subjects. The possibility of HHV-6 transmission from a healthy blood donor with high HHV-6 viral load to an immunocompromised recipient cannot be excluded but it does not warrant broad testing for HHV-6. Further studies are needed, to clarify the potential risk of HHV-6 transmission from seropositive donors especially with high HHV-6 viral load but after the adoption of a common accredited detection method .