The high percentages of nucleotide identity were in accordance with the single clustering of all 2009-2010 strains in the phylogenetic tree of HA and NA genes (Fig. 2) , without temporal or geographical distribution. It is interesting to note that the overall genetic diversity among 2009 H1N1pdm was less than typically observed among seasonal influenza. This is in accordance with its short period of time of circulation in humans [13] . The single clustering of 2009 H1N1pdm observed in this report, however, is in contrast with other studies [14] , in which the authors observe differences by using small datasets of sequences. The single clustering of 2009 H1N1pdm, furthermore, agrees with serological data in which it was observed that antigenically, the new pandemic viruses were all similar [6] , and thus not requiring a new update of the vaccine (strain A/California/07/2009) until now.