Survey of Viral Reactivations in Elite Athletes: A Case-Control Study

Exercise-induced immune perturbations have been proposed to increase susceptibility toviral infections. We investigated the replication of persisting viruses as indicators of immune functionin elite cross-country skiers after ten months of sustained high-performance exercise. The virusesevaluated, nine human herpesviruses (HHVs) and torque teno virus (TTV), are typically restrainedin health but replicate actively in immunosuppressed individuals. We collected sera from 27 Finnishelite cross-country skiers at the end of the competition’s season and 27 matched controls who performmoderate exercise. We quantified all the HHVs and—TTV via highly sensitive qPCRs. To verifyequal past exposures between the groups, we assessed the IgG antibody prevalences toward HHV-4(Epstein–Barr virus, EBV) and HHV-5 (human cytomegalovirus, HCMV). We found equal TTV DNAprevalences in athletes (63%) and controls (63%) and loads with respective geometric means of1.7×103and 1.2×103copies/mL of serum. Overall, the copy numbers were low and consistentwith those of healthy individuals. Neither of the groups presented with herpesvirus viremia despitesimilar past exposures to HHVs (seroprevalences of EBV 70% vs. 78% and HCMV 52% vs. 44%in athletes and controls, respectively). We found no evidence of increased replication of persistentviruses in elite athletes, arguing against impaired viral immunity due to high-performance exercise