Mutational scan along the HBV genome. Nucleotide substitutions uniquely present in EU155893 HBV DNA (d4, thick grey line, occult infection) and in control AB205128 HBV DNA (thick black line, overt infection) are compared with 89 HBV DNAs of genotype D and plotted cumulatively along the HBV genome. Steep slopes at the a-determinant (1), the oligonucleotide 895–909 (2) and the central part of C (3) indicate the relatively high divergence of these regions in d4 HBV. Thin grey lines represent characteristic mutations in the available HBV sequences from blood samples of the other donors with occult HBV infection. Numbering starts from the conventional EcoR1 site between S1 and S2. A map of HBV genome organization is provided on top of the figure.