Sera from patients infected with a virus contain tell-tale signs of the infection in the form of antibodies. To use these for screening, peptide ligands have to be identified that will bind to all patients' sera. Using sera from several patients infected with hepatitis C virus, Bartoli et al. have developed a method for screening phage-displayed peptide libraries that includes a DNA hybridization step. By using this second-tier DNA based screening step, phage displaying peptides that are common to multiple HCV-specific sera—which could be used for viral screening—were easily obtained (see p. 1068).