TTV detection and quantification.
TTV DNA was quantified in nasopharyngeal swabbing samples used for SARS-Cov-2 RT-PCR. DNA was extracted using the QiaSymphony instrument (Qiagen, Hilden, Germany) from 200 µl of Universal Transport Medium. Quantification was carried out by real-time PCR (TTV R-Gene, bioMérieux, Marcy l’étoile, France) on an ABI 7500 instrument (ThermoFisher, Waltham, MA) according to manufacturer instructions. The limit of quantification is 250 copies per mL.