Phylogenetic trees of the 5′ noncoding region of HCV showing the genotypes identified in 3 individuals with prolonged antibody-undetectable periods. Patient specimens, consensus sequences, time in months before (−) and after (+) HCV seroconversion, and the 6 major consensus sequences are indicated. The trees were bootstrapped 500 times and the numbers represent the percentages of the 500 bootstraps where those branches were the same. The horizontal distances are represented by the scale bar in the lower part of the figure and the distance is indicated.