For the quantification of virus before and after Phi29amplification, virus-specific real-time PCR's were performed. These were in-house assays for HSV1, HSV2, HPV6, HPV16, BKV, Rota A, Astrovirus, EV and RSV. For the detection of human gDNA, an in-house assay for b-actin was used (95uC for 15 minutes, 40 cycles of 95uC for 15 seconds and 55uC for 1 minute; Forward primer: CTC TTC CAG CCT TCC TTC CT, Reverse primer: AGC ACT GTG TTG GCG TAC AG, Probe: Yakima Yellow-TGG AGT CCT GTG GCA TCC ACG A-BHQ. In addition, previously published assays were used for JCV [23] , HCV [21] and Sapovirus [22] . For the multi-HPV (6, 16, 53, 61) positive sample (determined in the routine by ClartH HPV2 microarray, Genomica), only HPV 6-and 16-specific PCR's were performed before and after Phi29-amplification. For the quantitative analysis of BKV, we used an in-house standard containing 20,000-2610 7 copies/ml. For the confirmation of additional viruses found by microarray analysis, in-house real-time PCR's were used for HPV103, Picobirnavirus, Rota C and Dengue subtypes (1, 2, 3 and 4), and previously published assays for JCV [23] , GB virus type C (GBV-C) [24] and Human Adenovirus C (HAdV-C) [25] . Thermal cycling was performed in a thermal cycler (Mx3005P (Stratagene) or ABI7900 (Applied Biosystems)). Fold difference was calculated from DCt obtained from real-time PCR results before and after Phi29-amplification, combined with dilution factors for each sample. In doing so, we also made the assumption that a change in Ct-value was equivalent to a doubling of target DNA.