Kaplan-Meier curves of probability of overall mortality after allogeneic HCT stratified by recipient–donor iciHHV-6 status. Probability of overall mortality (A) within the first 100 days post-HCT and (B) between day 101 and 5 years post-HCT. Within the first 100 days, there were 673 deaths (16%) among recipient negative–donor negative pairs, 8 deaths (17%) among recipient positive–donor negative pairs, 3 deaths (11%) among recipient negative–donor positive pairs, and 3 deaths (23%) among recipient positive–donor positive pairs. Between day 101 and 5 years, there were 1746 deaths (41%) among recipient negative–donor negative pairs, 15 deaths (32%) among recipient positive–donor negative pairs, 12 deaths (44%) among recipient negative–donor positive pairs, and 6 deaths (46%) among recipient positive–donor positive pairs.