Visual representations of VirScan scores over time in HCT pairs. (A) Aggregated heat map with 5 longitudinal samples, grouped by CMV serostatus of the HCT donor-recipient pair (D⁺/R⁺, D⁻/R⁺, D⁺/R⁻, D⁻/R⁻). Colors correspond to mean numbers of epitopes recognized within all samples belonging to that group (range <1 to 40 mean recognized epitopes). White designates no epitope recognition in any sample (mean = 0). Attention to CMV row (red label) shows distinct differences over time by CMV serostatus as determined by Food and Drug Administration–approved serology. A threshold of 6 VirScan epitopes performs optimally against clinical serology (B) CMV epitopes detected by VirScan vs clinical reactivation of CMV in a D⁻/R⁺ recipient who also received high daily doses of systemic steroids for GVHD. Each quantitative antigenemia value is depicted by a purple dot and daily steroid dose by the orange line. (C) Acquisition of respiratory syncytial virus (RSV) epitopes during lower respiratory tract infection in a susceptible patient (D⁻/R⁺ for RSV); RSV was detected in upper and lower respiratory samples by direct fluorescent antibody (DFA) on 4 individual samples (DFA in clinical use, shown with asterisks). HPV, human papillomavirus; MPV, human metapneumovirus; HHV, human herpesvirus; SARS, severe acute respiratory syndrome; pre-D, pre-HCT donor sample; pre-R, pre-HCT recipient sample.