The online tool presents two query options to the user; entering gene segment sequence(s) or genotype sequence(s) (Figure 1) . The segment query 'Determine Individual Gene Segment Lineage' is used to identify the lineage of a viral gene segment of interest, for example PB2. In this case, the input FASTA file can contain one or many sequences, but all must correspond to the same gene segment. To analyze data sets from more than one gene simultaneously; e.g. both the PB1 and PB2, the user must first enter the number of different gene segments and then provide each sequence data set in a separate FASTA file.